MINOR: Clean up group-coordinator (#19008)

Given that now we support Java 17 on our brokers, this PR replace the
use of :
- `Collections.singletonList()` and `Collections.emptyList()` with
`List.of()`
- `Collections.singletonMap()` and `Collections.emptyMap()` with
`Map.of()`
- `Collections.singleton()` and `Collections.emptySet()` with `Set.of()`

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupCoordinatorRecordHelpers.java

@@ -477,7 +477,7 @@ public class GroupCoordinatorRecordHelpers {
                     .setGeneration(0)
                     .setLeader(null)
                     .setCurrentStateTimestamp(group.currentStateTimestampOrDefault())
-                    .setMembers(Collections.emptyList()),
+                    .setMembers(List.of()),
                 GROUP_METADATA_VALUE_VERSION
             )
         );

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupCoordinatorService.java

@@ -115,7 +115,6 @@ import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.IntSupplier;
-import java.util.stream.Collectors;
 
 import static org.apache.kafka.coordinator.common.runtime.CoordinatorOperationExceptionHelper.handleOperationException;
 
@@ -400,7 +399,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
             return CompletableFuture.completedFuture(
                 new StreamsGroupHeartbeatResult(
                     new StreamsGroupHeartbeatResponseData().setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code()),
-                    Collections.emptyMap()
+                    Map.of()
                 )
             );
         }
@@ -419,7 +418,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                     new StreamsGroupHeartbeatResponseData()
                         .setErrorCode(error.code())
                         .setErrorMessage(message),
-                    Collections.emptyMap()
+                    Map.of()
                 ),
             log
         ));
@@ -633,7 +632,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                              .setMemberId(member.memberId())
                              .setGroupInstanceId(member.groupInstanceId())
                              .setErrorCode(Errors.UNKNOWN_MEMBER_ID.code()))
-                         .collect(Collectors.toList());
+                         .toList();
                     return new LeaveGroupResponseData()
                         .setMembers(memberResponses);
                 } else {
@@ -671,7 +670,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
             exception -> {
                 exception = Errors.maybeUnwrapException(exception);
                 if (exception instanceof NotCoordinatorException) {
-                    return Collections.emptyList();
+                    return List.of();
                 } else {
                     throw new CompletionException(exception);
                 }
@@ -714,7 +713,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                     .computeIfAbsent(topicPartitionFor(groupId), __ -> new ArrayList<>())
                     .add(groupId);
             } else {
-                futures.add(CompletableFuture.completedFuture(Collections.singletonList(
+                futures.add(CompletableFuture.completedFuture(List.of(
                     new ConsumerGroupDescribeResponseData.DescribedGroup()
                         .setGroupId(null)
                         .setErrorCode(Errors.INVALID_GROUP_ID.code())
@@ -766,7 +765,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                     .computeIfAbsent(topicPartitionFor(groupId), __ -> new ArrayList<>())
                     .add(groupId);
             } else {
-                futures.add(CompletableFuture.completedFuture(Collections.singletonList(
+                futures.add(CompletableFuture.completedFuture(List.of(
                     new StreamsGroupDescribeResponseData.DescribedGroup()
                         .setGroupId(null)
                         .setErrorCode(Errors.INVALID_GROUP_ID.code())
@@ -817,7 +816,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                     .computeIfAbsent(topicPartitionFor(groupId), __ -> new ArrayList<>())
                     .add(groupId);
             } else {
-                futures.add(CompletableFuture.completedFuture(Collections.singletonList(
+                futures.add(CompletableFuture.completedFuture(List.of(
                     new ShareGroupDescribeResponseData.DescribedGroup()
                         .setGroupId(null)
                         .setErrorCode(Errors.INVALID_GROUP_ID.code())
@@ -866,7 +865,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
         groupIds.forEach(groupId -> {
             // For backwards compatibility, we support DescribeGroups for the empty group id.
             if (groupId == null) {
-                futures.add(CompletableFuture.completedFuture(Collections.singletonList(
+                futures.add(CompletableFuture.completedFuture(List.of(
                     new DescribeGroupsResponseData.DescribedGroup()
                         .setGroupId(null)
                         .setErrorCode(Errors.INVALID_GROUP_ID.code())
@@ -1149,7 +1148,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                 topicPartitionFor(request.groupId()),
                 Duration.ofMillis(config.offsetCommitTimeoutMs()),
                 coordinator -> new CoordinatorResult<>(
-                    Collections.emptyList(),
+                    List.of(),
                     coordinator.fetchOffsets(request, Long.MAX_VALUE)
                 )
             ).exceptionally(exception -> handleOffsetFetchException(
@@ -1204,7 +1203,7 @@ public class GroupCoordinatorService implements GroupCoordinator {
                 topicPartitionFor(request.groupId()),
                 Duration.ofMillis(config.offsetCommitTimeoutMs()),
                 coordinator -> new CoordinatorResult<>(
-                    Collections.emptyList(),
+                    List.of(),
                     coordinator.fetchAllOffsets(request, Long.MAX_VALUE)
                 )
             ).exceptionally(exception -> handleOffsetFetchException(

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupMetadataManager.java

@@ -456,7 +456,7 @@ public class GroupMetadataManager {
      * Package private for testing.
      */
     static final CoordinatorResult<Void, CoordinatorRecord> EMPTY_RESULT =
-        new CoordinatorResult<>(Collections.emptyList(), CompletableFuture.completedFuture(null), false);
+        new CoordinatorResult<>(List.of(), CompletableFuture.completedFuture(null), false);
 
     /**
      * The share group partition assignor.
@@ -574,7 +574,7 @@ public class GroupMetadataManager {
         return groupStream
             .filter(combinedFilter)
             .map(group -> group.asListedGroup(committedOffset))
-            .collect(Collectors.toList());
+            .toList();
     }
 
     /**
@@ -701,7 +701,7 @@ public class GroupMetadataManager {
                         .setProtocolData(group.protocolName().get())
                         .setMembers(group.allMembers().stream()
                             .map(member -> member.describe(group.protocolName().get()))
-                            .collect(Collectors.toList())
+                            .toList()
                         )
                     );
                 } else {
@@ -711,7 +711,7 @@ public class GroupMetadataManager {
                         .setProtocolType(group.protocolType().orElse(""))
                         .setMembers(group.allMembers().stream()
                             .map(ClassicGroupMember::describeNoMetadata)
-                            .collect(Collectors.toList())
+                            .toList()
                         )
                     );
                 }
@@ -1792,7 +1792,7 @@ public class GroupMetadataManager {
             .map(keyValue -> new ConsumerGroupHeartbeatResponseData.TopicPartitions()
                 .setTopicId(keyValue.getKey())
                 .setPartitions(new ArrayList<>(keyValue.getValue())))
-            .collect(Collectors.toList());
+            .toList();
     }
 
     private List<ShareGroupHeartbeatResponseData.TopicPartitions> fromShareGroupAssignmentMap(
@@ -1802,7 +1802,7 @@ public class GroupMetadataManager {
             .map(keyValue -> new ShareGroupHeartbeatResponseData.TopicPartitions()
                 .setTopicId(keyValue.getKey())
                 .setPartitions(new ArrayList<>(keyValue.getValue())))
-            .collect(Collectors.toList());
+            .toList();
     }
 
     /**
@@ -2038,7 +2038,7 @@ public class GroupMetadataManager {
                 group,
                 memberId,
                 -1,
-                Collections.emptyList(),
+                List.of(),
                 true,
                 true
             );
@@ -2048,7 +2048,7 @@ public class GroupMetadataManager {
                 memberId,
                 -1,
                 instanceId,
-                Collections.emptyList(),
+                List.of(),
                 isUnknownMember,
                 true,
                 records
@@ -2145,7 +2145,7 @@ public class GroupMetadataManager {
         if (downgrade) {
             convertToClassicGroup(
                 group,
-                Collections.emptySet(),
+                Set.of(),
                 updatedMember,
                 records
             );
@@ -2727,7 +2727,7 @@ public class GroupMetadataManager {
         if (exception != null) {
             log.error("[GroupId {}] Couldn't update regular expression due to: {}",
                 groupId, exception.getMessage());
-            return new CoordinatorResult<>(Collections.emptyList());
+            return new CoordinatorResult<>(List.of());
         }
 
         if (log.isDebugEnabled()) {
@@ -3197,11 +3197,11 @@ public class GroupMetadataManager {
         // We will write a member epoch of -2 for this departing static member.
         ConsumerGroupMember leavingStaticMember = new ConsumerGroupMember.Builder(member)
             .setMemberEpoch(LEAVE_GROUP_STATIC_MEMBER_EPOCH)
-            .setPartitionsPendingRevocation(Collections.emptyMap())
+            .setPartitionsPendingRevocation(Map.of())
             .build();
 
         return new CoordinatorResult<>(
-            Collections.singletonList(newConsumerGroupCurrentAssignmentRecord(group.groupId(), leavingStaticMember)),
+            List.of(newConsumerGroupCurrentAssignmentRecord(group.groupId(), leavingStaticMember)),
             new ConsumerGroupHeartbeatResponseData()
                 .setMemberId(member.memberId())
                 .setMemberEpoch(LEAVE_GROUP_STATIC_MEMBER_EPOCH)
@@ -3266,7 +3266,7 @@ public class GroupMetadataManager {
     ) {
         if (members.isEmpty()) {
             // No members to fence. Don't bump the group epoch.
-            return new CoordinatorResult<>(Collections.emptyList(), response);
+            return new CoordinatorResult<>(List.of(), response);
         }
 
         List<CoordinatorRecord> records = new ArrayList<>();
@@ -3563,7 +3563,7 @@ public class GroupMetadataManager {
                 groupId, memberId);
         }
 
-        return new CoordinatorResult<>(Collections.emptyList());
+        return new CoordinatorResult<>(List.of());
     }
 
     /**
@@ -3596,7 +3596,7 @@ public class GroupMetadataManager {
                 groupId, memberId);
         }
 
-        return new CoordinatorResult<>(Collections.emptyList());
+        return new CoordinatorResult<>(List.of());
     }
 
     /**
@@ -3629,7 +3629,7 @@ public class GroupMetadataManager {
                 groupId, memberId);
         }
 
-        return new CoordinatorResult<>(Collections.emptyList());
+        return new CoordinatorResult<>(List.of());
     }
 
     /**
@@ -3715,7 +3715,7 @@ public class GroupMetadataManager {
                 } else {
                     log.debug("[GroupId {}] Ignoring rebalance timeout for {} because the member " +
                         "left the epoch {}.", groupId, memberId, memberEpoch);
-                    return new CoordinatorResult<>(Collections.emptyList());
+                    return new CoordinatorResult<>(List.of());
                 }
             } catch (GroupIdNotFoundException ex) {
                 log.debug("[GroupId {}] Could not fence {}} because the group does not exist.",
@@ -3725,7 +3725,7 @@ public class GroupMetadataManager {
                     groupId, memberId);
             }
 
-            return new CoordinatorResult<>(Collections.emptyList());
+            return new CoordinatorResult<>(List.of());
         });
     }
 
@@ -3758,7 +3758,7 @@ public class GroupMetadataManager {
                 } else {
                     log.debug("[GroupId {}] Ignoring rebalance timeout for {} because the member " +
                         "is not in epoch {} anymore.", groupId, memberId, memberEpoch);
-                    return new CoordinatorResult<>(Collections.emptyList());
+                    return new CoordinatorResult<>(List.of());
                 }
             } catch (GroupIdNotFoundException ex) {
                 log.debug("[GroupId {}] Could not fence {}} because the group does not exist.",
@@ -3768,7 +3768,7 @@ public class GroupMetadataManager {
                     groupId, memberId);
             }
 
-            return new CoordinatorResult<>(Collections.emptyList());
+            return new CoordinatorResult<>(List.of());
         });
     }
 
@@ -3935,7 +3935,7 @@ public class GroupMetadataManager {
         if (streamsGroup.topology().isPresent()) {
             oldSubscribedTopicNames = streamsGroup.topology().get().requiredTopics();
         } else {
-            oldSubscribedTopicNames = Collections.emptySet();
+            oldSubscribedTopicNames = Set.of();
         }
         if (value != null) {
             StreamsTopology topology = StreamsTopology.fromRecord(value);
@@ -3943,7 +3943,7 @@ public class GroupMetadataManager {
             Set<String> newSubscribedTopicNames = topology.requiredTopics();
             updateGroupsByTopics(groupId, oldSubscribedTopicNames, newSubscribedTopicNames);
         } else {
-            updateGroupsByTopics(groupId, oldSubscribedTopicNames, Collections.emptySet());
+            updateGroupsByTopics(groupId, oldSubscribedTopicNames, Set.of());
             streamsGroup.setTopology(null);
         }
     }
@@ -4039,7 +4039,7 @@ public class GroupMetadataManager {
      */
     public Set<String> groupsSubscribedToTopic(String topicName) {
         Set<String> groups = groupsByTopics.get(topicName);
-        return groups != null ? groups : Collections.emptySet();
+        return groups != null ? groups : Set.of();
     }
 
     /**
@@ -4180,7 +4180,7 @@ public class GroupMetadataManager {
             });
             group.setSubscriptionMetadata(subscriptionMetadata);
         } else {
-            group.setSubscriptionMetadata(Collections.emptyMap());
+            group.setSubscriptionMetadata(Map.of());
         }
     }
 
@@ -4287,8 +4287,8 @@ public class GroupMetadataManager {
             ConsumerGroupMember newMember = new ConsumerGroupMember.Builder(oldMember)
                 .setMemberEpoch(LEAVE_GROUP_MEMBER_EPOCH)
                 .setPreviousMemberEpoch(LEAVE_GROUP_MEMBER_EPOCH)
-                .setAssignedPartitions(Collections.emptyMap())
+                .setAssignedPartitions(Map.of())
-                .setPartitionsPendingRevocation(Collections.emptyMap())
+                .setPartitionsPendingRevocation(Map.of())
                 .build();
             group.updateMember(newMember);
         }
@@ -4395,7 +4395,7 @@ public class GroupMetadataManager {
             });
             streamsGroup.setPartitionMetadata(partitionMetadata);
         } else {
-            streamsGroup.setPartitionMetadata(Collections.emptyMap());
+            streamsGroup.setPartitionMetadata(Map.of());
         }
     }
 
@@ -4657,7 +4657,7 @@ public class GroupMetadataManager {
             );
             group.setSubscriptionMetadata(subscriptionMetadata);
         } else {
-            group.setSubscriptionMetadata(Collections.emptyMap());
+            group.setSubscriptionMetadata(Map.of());
         }
     }
 
@@ -4735,7 +4735,7 @@ public class GroupMetadataManager {
             ShareGroupMember newMember = new ShareGroupMember.Builder(oldMember)
                     .setMemberEpoch(LEAVE_GROUP_MEMBER_EPOCH)
                     .setPreviousMemberEpoch(LEAVE_GROUP_MEMBER_EPOCH)
-                    .setAssignedPartitions(Collections.emptyMap())
+                    .setAssignedPartitions(Map.of())
                     .build();
             group.updateMember(newMember);
         }
@@ -5410,7 +5410,7 @@ public class GroupMetadataManager {
                     // for the current generation.
                     responseFuture.complete(new JoinGroupResponseData()
                         .setMembers(group.isLeader(memberId) ?
-                            group.currentClassicGroupMembers() : Collections.emptyList())
+                            group.currentClassicGroupMembers() : List.of())
                         .setMemberId(memberId)
                         .setGenerationId(group.generationId())
                         .setProtocolName(group.protocolName().orElse(null))
@@ -5455,7 +5455,7 @@ public class GroupMetadataManager {
                     // For followers with no actual change to their metadata, just return group information
                     // for the current generation which will allow them to issue SyncGroup.
                     responseFuture.complete(new JoinGroupResponseData()
-                        .setMembers(Collections.emptyList())
+                        .setMembers(List.of())
                         .setMemberId(memberId)
                         .setGenerationId(group.generationId())
                         .setProtocolName(group.protocolName().orElse(null))
@@ -5562,8 +5562,8 @@ public class GroupMetadataManager {
                     }
                 });
 
-                List<CoordinatorRecord> records = Collections.singletonList(GroupCoordinatorRecordHelpers.newGroupMetadataRecord(
+                List<CoordinatorRecord> records = List.of(GroupCoordinatorRecordHelpers.newGroupMetadataRecord(
-                    group, Collections.emptyMap()));
+                    group, Map.of()));
 
                 return new CoordinatorResult<>(records, appendFuture, false);
 
@@ -5573,7 +5573,7 @@ public class GroupMetadataManager {
 
                 // Complete the awaiting join group response future for all the members after rebalancing
                 group.allMembers().forEach(member -> {
-                    List<JoinGroupResponseData.JoinGroupResponseMember> members = Collections.emptyList();
+                    List<JoinGroupResponseData.JoinGroupResponseMember> members = List.of();
                     if (group.isLeader(member.memberId())) {
                         members = group.currentClassicGroupMembers();
                     }
@@ -6204,7 +6204,7 @@ public class GroupMetadataManager {
                         boolean isLeader = group.isLeader(newMemberId);
 
                         group.completeJoinFuture(newMember, new JoinGroupResponseData()
-                            .setMembers(isLeader ? group.currentClassicGroupMembers() : Collections.emptyList())
+                            .setMembers(isLeader ? group.currentClassicGroupMembers() : List.of())
                             .setMemberId(newMemberId)
                             .setGenerationId(group.generationId())
                             .setProtocolName(group.protocolName().orElse(null))
@@ -6224,7 +6224,7 @@ public class GroupMetadataManager {
                     }
                 });
 
-                List<CoordinatorRecord> records = Collections.singletonList(
+                List<CoordinatorRecord> records = List.of(
                     GroupCoordinatorRecordHelpers.newGroupMetadataRecord(group, groupAssignment)
                 );
 
@@ -6371,7 +6371,7 @@ public class GroupMetadataManager {
                     }
                 });
 
-                List<CoordinatorRecord> records = Collections.singletonList(
+                List<CoordinatorRecord> records = List.of(
                     GroupCoordinatorRecordHelpers.newGroupMetadataRecord(group, assignment)
                 );
                 return new CoordinatorResult<>(records, appendFuture, false);
@@ -6433,7 +6433,7 @@ public class GroupMetadataManager {
             }
         });
 
-        return new CoordinatorResult<>(Collections.emptyList(), appendFuture, false);
+        return new CoordinatorResult<>(List.of(), appendFuture, false);
     }
 
     /**
@@ -6586,14 +6586,14 @@ public class GroupMetadataManager {
         switch (group.currentState()) {
             case EMPTY:
                 return new CoordinatorResult<>(
-                    Collections.emptyList(),
+                    List.of(),
                     new HeartbeatResponseData().setErrorCode(Errors.UNKNOWN_MEMBER_ID.code())
                 );
 
             case PREPARING_REBALANCE:
                 rescheduleClassicGroupMemberHeartbeat(group, group.member(request.memberId()));
                 return new CoordinatorResult<>(
-                    Collections.emptyList(),
+                    List.of(),
                     new HeartbeatResponseData().setErrorCode(Errors.REBALANCE_IN_PROGRESS.code())
                 );
 
@@ -6604,7 +6604,7 @@ public class GroupMetadataManager {
                 // normal heartbeat requests and reset the timer
                 rescheduleClassicGroupMemberHeartbeat(group, group.member(request.memberId()));
                 return new CoordinatorResult<>(
-                    Collections.emptyList(),
+                    List.of(),
                     new HeartbeatResponseData()
                 );
 
@@ -6687,7 +6687,7 @@ public class GroupMetadataManager {
         }
 
         return new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
             new HeartbeatResponseData().setErrorCode(error.code())
         );
     }
@@ -6827,7 +6827,7 @@ public class GroupMetadataManager {
     ) throws UnknownMemberIdException {
         if (group.isInState(DEAD)) {
             return new CoordinatorResult<>(
-                Collections.emptyList(),
+                List.of(),
                 new LeaveGroupResponseData()
                     .setErrorCode(COORDINATOR_NOT_AVAILABLE.code())
             );
@@ -6897,7 +6897,7 @@ public class GroupMetadataManager {
         List<String> validLeaveGroupMembers = memberResponses.stream()
             .filter(response -> response.errorCode() == Errors.NONE.code())
             .map(MemberResponse::memberId)
-            .collect(Collectors.toList());
+            .toList();
 
         String reason = "explicit `LeaveGroup` request for (" + String.join(", ", validLeaveGroupMembers) + ") members.";
         CoordinatorResult<Void, CoordinatorRecord> coordinatorResult = EMPTY_RESULT;

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/OffsetMetadataManager.java

@@ -55,7 +55,6 @@ import org.apache.kafka.timeline.TimelineHashSet;
 import org.slf4j.Logger;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -799,7 +798,7 @@ public class OffsetMetadataManager {
         } catch (GroupIdNotFoundException ex) {
             return new OffsetFetchResponseData.OffsetFetchResponseGroup()
                 .setGroupId(request.groupId())
-                .setTopics(Collections.emptyList());
+                .setTopics(List.of());
         }
 
         final List<OffsetFetchResponseData.OffsetFetchResponseTopics> topicResponses = new ArrayList<>();

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/RangeAssignor.java

@@ -28,7 +28,6 @@ import org.apache.kafka.coordinator.group.api.assignor.SubscriptionType;
 import org.apache.kafka.coordinator.group.modern.MemberAssignmentImpl;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -306,7 +305,7 @@ public class RangeAssignor implements ConsumerGroupPartitionAssignor {
         SubscribedTopicDescriber subscribedTopicDescriber
     ) throws PartitionAssignorException {
         if (groupSpec.memberIds().isEmpty()) {
-            return new GroupAssignment(Collections.emptyMap());
+            return new GroupAssignment(Map.of());
         } else if (groupSpec.subscriptionType() == SubscriptionType.HOMOGENEOUS) {
             return assignHomogeneousGroup(groupSpec, subscribedTopicDescriber);
         } else {

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/SimpleAssignor.java

@@ -29,7 +29,6 @@ import org.apache.kafka.server.common.TopicIdPartition;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -227,7 +226,7 @@ public class SimpleAssignor implements ShareGroupPartitionAssignor {
         // When combining current assignment, we need to only consider the member topic subscription in current assignment
         // which is being subscribed in the new assignment as well.
         currentAssignment.forEach((topicIdPartition, members) -> members.forEach(member -> {
-            if (topicToMemberSubscription.getOrDefault(topicIdPartition.topicId(), Collections.emptySet()).contains(member)
+            if (topicToMemberSubscription.getOrDefault(topicIdPartition.topicId(), Set.of()).contains(member)
                 && !newAssignment.containsKey(topicIdPartition))
                 finalAssignment.computeIfAbsent(member, k -> new HashSet<>()).add(topicIdPartition);
         }));

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/UniformAssignor.java

@@ -25,7 +25,7 @@ import org.apache.kafka.coordinator.group.api.assignor.SubscribedTopicDescriber;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.Collections;
+import java.util.Map;
 
 import static org.apache.kafka.coordinator.group.api.assignor.SubscriptionType.HOMOGENEOUS;
 
@@ -73,7 +73,7 @@ public class UniformAssignor implements ConsumerGroupPartitionAssignor {
         SubscribedTopicDescriber subscribedTopicDescriber
     ) throws PartitionAssignorException {
         if (groupSpec.memberIds().isEmpty())
-            return new GroupAssignment(Collections.emptyMap());
+            return new GroupAssignment(Map.of());
 
         if (groupSpec.subscriptionType().equals(HOMOGENEOUS)) {
             LOG.debug("Detected that all members are subscribed to the same set of topics, invoking the "

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/UniformHeterogeneousAssignmentBuilder.java

@@ -27,7 +27,6 @@ import org.apache.kafka.coordinator.group.modern.MemberAssignmentImpl;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -238,7 +237,7 @@ public class UniformHeterogeneousAssignmentBuilder {
      */
     public GroupAssignment build() {
         if (subscribedTopicIds.isEmpty()) {
-            return new GroupAssignment(Collections.emptyMap());
+            return new GroupAssignment(Map.of());
         }
 
         maybeRevokePartitions();

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/UniformHomogeneousAssignmentBuilder.java

@@ -26,7 +26,6 @@ import org.apache.kafka.coordinator.group.modern.MemberAssignmentImpl;
 import org.apache.kafka.server.common.TopicIdPartition;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -109,7 +108,7 @@ public class UniformHomogeneousAssignmentBuilder {
      */
     public GroupAssignment build() throws PartitionAssignorException {
         if (subscribedTopicIds.isEmpty()) {
-            return new GroupAssignment(Collections.emptyMap());
+            return new GroupAssignment(Map.of());
         }
 
         // Compute the list of unassigned partitions.

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroup.java

@@ -46,7 +46,6 @@ import org.slf4j.Logger;
 
 import java.nio.ByteBuffer;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -551,7 +550,7 @@ public class ClassicGroup implements Group {
 
         // Fence potential duplicate member immediately if someone awaits join/sync future.
         JoinGroupResponseData joinGroupResponse = new JoinGroupResponseData()
-            .setMembers(Collections.emptyList())
+            .setMembers(List.of())
             .setMemberId(oldMemberId)
             .setProtocolName(null)
             .setProtocolType(null)
@@ -1150,7 +1149,7 @@ public class ClassicGroup implements Group {
             return Optional.empty();
         }
         if (members.isEmpty()) {
-            return Optional.of(Collections.emptySet());
+            return Optional.of(Set.of());
         }
 
         if (protocolName.isPresent()) {
@@ -1310,7 +1309,7 @@ public class ClassicGroup implements Group {
                 .setMemberId(member.memberId())
                 .setGroupInstanceId(member.groupInstanceId().orElse(null))
                 .setMetadata(member.metadata(protocolName.orElse(null))))
-            .collect(Collectors.toList());
+            .toList();
     }
 
     /**

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroupMember.java

@@ -28,7 +28,6 @@ import java.util.HashSet;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
-import java.util.stream.Collectors;
 
 /**
  * This class encapsulates a classic group member's metadata.
@@ -430,7 +429,7 @@ public class ClassicGroupMember {
             ", protocolType='" + protocolType + '\'' +
             ", supportedProtocols=" + supportedProtocols.stream()
                 .map(JoinGroupRequestProtocol::name)
-                .collect(Collectors.toList()) +
+                .toList() +
             ')';
     }
 }

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/metrics/GroupCoordinatorMetrics.java

@@ -126,49 +126,49 @@ public class GroupCoordinatorMetrics extends CoordinatorMetrics implements AutoC
             GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The total number of groups using the classic rebalance protocol.",
-            Collections.singletonMap(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.CLASSIC.toString())
+            Map.of(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.CLASSIC.toString())
         );
 
         consumerGroupCountMetricName = metrics.metricName(
             GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The total number of groups using the consumer rebalance protocol.",
-            Collections.singletonMap(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.CONSUMER.toString())
+            Map.of(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.CONSUMER.toString())
         );
 
         consumerGroupCountEmptyMetricName = metrics.metricName(
             CONSUMER_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of consumer groups in empty state.",
-            Collections.singletonMap(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.EMPTY.toString())
+            Map.of(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.EMPTY.toString())
         );
 
         consumerGroupCountAssigningMetricName = metrics.metricName(
             CONSUMER_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of consumer groups in assigning state.",
-            Collections.singletonMap(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.ASSIGNING.toString())
+            Map.of(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.ASSIGNING.toString())
         );
 
         consumerGroupCountReconcilingMetricName = metrics.metricName(
             CONSUMER_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of consumer groups in reconciling state.",
-            Collections.singletonMap(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.RECONCILING.toString())
+            Map.of(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.RECONCILING.toString())
         );
 
         consumerGroupCountStableMetricName = metrics.metricName(
             CONSUMER_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of consumer groups in stable state.",
-            Collections.singletonMap(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.STABLE.toString())
+            Map.of(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.STABLE.toString())
         );
 
         consumerGroupCountDeadMetricName = metrics.metricName(
             CONSUMER_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of consumer groups in dead state.",
-            Collections.singletonMap(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.DEAD.toString())
+            Map.of(CONSUMER_GROUP_COUNT_STATE_TAG, ConsumerGroupState.DEAD.toString())
         );
 
         shareGroupCountMetricName = metrics.metricName(
@@ -203,49 +203,49 @@ public class GroupCoordinatorMetrics extends CoordinatorMetrics implements AutoC
             GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The total number of groups using the streams rebalance protocol.",
-            Collections.singletonMap(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.STREAMS.toString())
+            Map.of(GROUP_COUNT_PROTOCOL_TAG, Group.GroupType.STREAMS.toString())
         );
 
         streamsGroupCountEmptyMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in empty state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.EMPTY.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.EMPTY.toString())
         );
 
         streamsGroupCountAssigningMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in assigning state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.ASSIGNING.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.ASSIGNING.toString())
         );
 
         streamsGroupCountReconcilingMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in reconciling state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.RECONCILING.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.RECONCILING.toString())
         );
 
         streamsGroupCountStableMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in stable state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.STABLE.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.STABLE.toString())
         );
 
         streamsGroupCountDeadMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in dead state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.DEAD.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.DEAD.toString())
         );
 
         streamsGroupCountNotReadyMetricName = metrics.metricName(
             STREAMS_GROUP_COUNT_METRIC_NAME,
             METRICS_GROUP,
             "The number of streams groups in not ready state.",
-            Collections.singletonMap(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.NOT_READY.toString())
+            Map.of(STREAMS_GROUP_COUNT_STATE_TAG, StreamsGroupState.NOT_READY.toString())
         );
 
         registerGauges();

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/metrics/GroupCoordinatorMetricsShard.java

@@ -29,7 +29,6 @@ import org.apache.kafka.timeline.TimelineLong;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicLong;
@@ -112,10 +111,10 @@ public class GroupCoordinatorMetricsShard implements CoordinatorMetricsShard {
         numOffsetsTimelineGaugeCounter = new TimelineGaugeCounter(new TimelineLong(snapshotRegistry), new AtomicLong(0));
         numClassicGroupsTimelineCounter = new TimelineGaugeCounter(new TimelineLong(snapshotRegistry), new AtomicLong(0));
 
-        this.classicGroupGauges = Collections.emptyMap();
+        this.classicGroupGauges = Map.of();
-        this.consumerGroupGauges = Collections.emptyMap();
+        this.consumerGroupGauges = Map.of();
-        this.streamsGroupGauges = Collections.emptyMap();
+        this.streamsGroupGauges = Map.of();
-        this.shareGroupGauges = Collections.emptyMap();
+        this.shareGroupGauges = Map.of();
 
         this.globalSensors = Objects.requireNonNull(globalSensors);
         this.topicPartition = Objects.requireNonNull(topicPartition);

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/Assignment.java

@@ -32,7 +32,7 @@ import java.util.stream.Collectors;
  * An immutable assignment for a member.
  */
 public class Assignment implements MemberAssignment {
-    public static final Assignment EMPTY = new Assignment(Collections.emptyMap());
+    public static final Assignment EMPTY = new Assignment(Map.of());
 
     /**
      * The partitions assigned to the member.

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/GroupSpecImpl.java

@@ -23,7 +23,6 @@ import org.apache.kafka.coordinator.group.api.assignor.MemberSubscription;
 import org.apache.kafka.coordinator.group.api.assignor.SubscriptionType;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 
@@ -104,7 +103,7 @@ public class GroupSpecImpl implements GroupSpec {
     public MemberAssignment memberAssignment(String memberId) {
         MemberSubscriptionAndAssignmentImpl member = members.get(memberId);
         if (member == null) {
-            return new MemberAssignmentImpl(Collections.emptyMap());
+            return new MemberAssignmentImpl(Map.of());
         }
         return member;
     }

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/ModernGroup.java

@@ -270,7 +270,7 @@ public abstract class ModernGroup<T extends ModernGroupMember> implements Group
     public void updateTargetAssignment(String memberId, Assignment newTargetAssignment) {
         updateInvertedTargetAssignment(
             memberId,
-            targetAssignment.getOrDefault(memberId, new Assignment(Collections.emptyMap())),
+            targetAssignment.getOrDefault(memberId, new Assignment(Map.of())),
             newTargetAssignment
         );
         targetAssignment.put(memberId, newTargetAssignment);
@@ -294,8 +294,8 @@ public abstract class ModernGroup<T extends ModernGroupMember> implements Group
         allTopicIds.addAll(newTargetAssignment.partitions().keySet());
 
         for (Uuid topicId : allTopicIds) {
-            Set<Integer> oldPartitions = oldTargetAssignment.partitions().getOrDefault(topicId, Collections.emptySet());
+            Set<Integer> oldPartitions = oldTargetAssignment.partitions().getOrDefault(topicId, Set.of());
-            Set<Integer> newPartitions = newTargetAssignment.partitions().getOrDefault(topicId, Collections.emptySet());
+            Set<Integer> newPartitions = newTargetAssignment.partitions().getOrDefault(topicId, Set.of());
 
             TimelineHashMap<Integer, String> topicPartitionAssignment = invertedTargetAssignment.computeIfAbsent(
                 topicId, k -> new TimelineHashMap<>(snapshotRegistry, Math.max(oldPartitions.size(), newPartitions.size()))

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/SubscribedTopicDescriberImpl.java

@@ -20,7 +20,6 @@ import org.apache.kafka.common.Uuid;
 import org.apache.kafka.coordinator.group.api.assignor.PartitionAssignor;
 import org.apache.kafka.coordinator.group.api.assignor.SubscribedTopicDescriber;
 
-import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -72,7 +71,7 @@ public class SubscribedTopicDescriberImpl implements SubscribedTopicDescriber {
      */
     @Override
     public Set<String> racksForPartition(Uuid topicId, int partition) {
-        return Collections.emptySet();
+        return Set.of();
     }
 
     @Override

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/TargetAssignmentBuilder.java

@@ -97,7 +97,7 @@ public abstract class TargetAssignmentBuilder<T extends ModernGroupMember, U ext
         /**
          * The resolved regular expressions.
          */
-        private Map<String, ResolvedRegularExpression> resolvedRegularExpressions = Collections.emptyMap();
+        private Map<String, ResolvedRegularExpression> resolvedRegularExpressions = Map.of();
 
         public ConsumerTargetAssignmentBuilder(
             String groupId,
@@ -248,12 +248,12 @@ public abstract class TargetAssignmentBuilder<T extends ModernGroupMember, U ext
     /**
      * The members in the group.
      */
-    private Map<String, T> members = Collections.emptyMap();
+    private Map<String, T> members = Map.of();
 
     /**
      * The subscription metadata.
      */
-    private Map<String, TopicMetadata> subscriptionMetadata = Collections.emptyMap();
+    private Map<String, TopicMetadata> subscriptionMetadata = Map.of();
 
     /**
      * The subscription type of the consumer group.
@@ -263,13 +263,13 @@ public abstract class TargetAssignmentBuilder<T extends ModernGroupMember, U ext
     /**
      * The existing target assignment.
      */
-    private Map<String, Assignment> targetAssignment = Collections.emptyMap();
+    private Map<String, Assignment> targetAssignment = Map.of();
 
     /**
      * Reverse lookup map representing topic partitions with
      * their current member assignments.
      */
-    private Map<Uuid, Map<Integer, String>> invertedTargetAssignment = Collections.emptyMap();
+    private Map<Uuid, Map<Integer, String>> invertedTargetAssignment = Map.of();
 
     /**
      * The topics image.

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroup.java

@@ -1151,7 +1151,7 @@ public class ConsumerGroup extends ModernGroup<ConsumerGroupMember> {
             // We should accept the empty assignment.
             Map<Uuid, Set<Integer>> assignedPartitions;
             if (Arrays.equals(classicGroupMember.assignment(), EMPTY_ASSIGNMENT)) {
-                assignedPartitions = Collections.emptyMap();
+                assignedPartitions = Map.of();
             } else {
                 ConsumerProtocolAssignment assignment = ConsumerProtocol.deserializeConsumerProtocolAssignment(
                     ByteBuffer.wrap(classicGroupMember.assignment())
@@ -1287,7 +1287,7 @@ public class ConsumerGroup extends ModernGroup<ConsumerGroupMember> {
         if (member.state() == MemberState.UNRELEASED_PARTITIONS) {
             for (Map.Entry<Uuid, Set<Integer>> entry : targetAssignment().get(member.memberId()).partitions().entrySet()) {
                 Uuid topicId = entry.getKey();
-                Set<Integer> assignedPartitions = member.assignedPartitions().getOrDefault(topicId, Collections.emptySet());
+                Set<Integer> assignedPartitions = member.assignedPartitions().getOrDefault(topicId, Set.of());
 
                 for (int partition : entry.getValue()) {
                     if (!assignedPartitions.contains(partition) && currentPartitionEpoch(topicId, partition) != -1) {

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroupMember.java

@@ -29,7 +29,6 @@ import org.apache.kafka.image.TopicImage;
 import org.apache.kafka.image.TopicsImage;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -62,11 +61,11 @@ public class ConsumerGroupMember extends ModernGroupMember {
         private int rebalanceTimeoutMs = -1;
         private String clientId = "";
         private String clientHost = "";
-        private Set<String> subscribedTopicNames = Collections.emptySet();
+        private Set<String> subscribedTopicNames = Set.of();
         private String subscribedTopicRegex = "";
         private String serverAssignorName = null;
-        private Map<Uuid, Set<Integer>> assignedPartitions = Collections.emptyMap();
+        private Map<Uuid, Set<Integer>> assignedPartitions = Map.of();
-        private Map<Uuid, Set<Integer>> partitionsPendingRevocation = Collections.emptyMap();
+        private Map<Uuid, Set<Integer>> partitionsPendingRevocation = Map.of();
         private ConsumerGroupMemberMetadataValue.ClassicMemberMetadata classicMemberMetadata = null;
 
         public Builder(String memberId) {
@@ -400,7 +399,7 @@ public class ConsumerGroupMember extends ModernGroupMember {
                 .setTopicPartitions(topicPartitionsFromMap(assignedPartitions, topicsImage)))
             .setTargetAssignment(new ConsumerGroupDescribeResponseData.Assignment()
                 .setTopicPartitions(topicPartitionsFromMap(
-                    targetAssignment != null ? targetAssignment.partitions() : Collections.emptyMap(),
+                    targetAssignment != null ? targetAssignment.partitions() : Map.of(),
                     topicsImage
                 )))
             .setClientHost(clientHost)

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/CurrentAssignmentBuilder.java

@@ -22,7 +22,6 @@ import org.apache.kafka.common.message.ConsumerGroupHeartbeatRequestData;
 import org.apache.kafka.coordinator.group.modern.Assignment;
 import org.apache.kafka.coordinator.group.modern.MemberState;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -204,7 +203,7 @@ public class CurrentAssignmentBuilder {
 
         for (ConsumerGroupHeartbeatRequestData.TopicPartitions topicPartitions : ownedTopicPartitions) {
             Set<Integer> partitionsPendingRevocation =
-                assignment.getOrDefault(topicPartitions.topicId(), Collections.emptySet());
+                assignment.getOrDefault(topicPartitions.topicId(), Set.of());
 
             for (Integer partitionId : topicPartitions.partitions()) {
                 if (partitionsPendingRevocation.contains(partitionId)) {
@@ -238,9 +237,9 @@ public class CurrentAssignmentBuilder {
 
         for (Uuid topicId : allTopicIds) {
             Set<Integer> target = targetAssignment.partitions()
-                .getOrDefault(topicId, Collections.emptySet());
+                .getOrDefault(topicId, Set.of());
             Set<Integer> currentAssignedPartitions = memberAssignedPartitions
-                .getOrDefault(topicId, Collections.emptySet());
+                .getOrDefault(topicId, Set.of());
 
             // New Assigned Partitions = Previous Assigned Partitions ∩ Target
             Set<Integer> assignedPartitions = new HashSet<>(currentAssignedPartitions);
@@ -295,7 +294,7 @@ public class CurrentAssignmentBuilder {
                 .setState(newState)
                 .updateMemberEpoch(targetAssignmentEpoch)
                 .setAssignedPartitions(newAssignedPartitions)
-                .setPartitionsPendingRevocation(Collections.emptyMap())
+                .setPartitionsPendingRevocation(Map.of())
                 .build();
         } else if (hasUnreleasedPartitions) {
             // If there are no partitions to be revoked nor to be assigned but some
@@ -305,7 +304,7 @@ public class CurrentAssignmentBuilder {
                 .setState(MemberState.UNRELEASED_PARTITIONS)
                 .updateMemberEpoch(targetAssignmentEpoch)
                 .setAssignedPartitions(newAssignedPartitions)
-                .setPartitionsPendingRevocation(Collections.emptyMap())
+                .setPartitionsPendingRevocation(Map.of())
                 .build();
         } else {
             // Otherwise, the member transitions to the target epoch and to the
@@ -314,7 +313,7 @@ public class CurrentAssignmentBuilder {
                 .setState(MemberState.STABLE)
                 .updateMemberEpoch(targetAssignmentEpoch)
                 .setAssignedPartitions(newAssignedPartitions)
-                .setPartitionsPendingRevocation(Collections.emptyMap())
+                .setPartitionsPendingRevocation(Map.of())
                 .build();
         }
     }

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/ResolvedRegularExpression.java

@@ -24,7 +24,7 @@ import java.util.Set;
  * The metadata associated with a regular expression in a Consumer Group.
  */
 public class ResolvedRegularExpression {
-    public static final ResolvedRegularExpression EMPTY = new ResolvedRegularExpression(Collections.emptySet(), -1L, -1L);
+    public static final ResolvedRegularExpression EMPTY = new ResolvedRegularExpression(Set.of(), -1L, -1L);
 
     /**
      * The set of resolved topics.

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/share/ShareGroupMember.java

@@ -27,7 +27,6 @@ import org.apache.kafka.image.TopicImage;
 import org.apache.kafka.image.TopicsImage;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -56,8 +55,8 @@ public class ShareGroupMember extends ModernGroupMember {
         private String rackId = null;
         private String clientId = "";
         private String clientHost = "";
-        private Set<String> subscribedTopicNames = Collections.emptySet();
+        private Set<String> subscribedTopicNames = Set.of();
-        private Map<Uuid, Set<Integer>> assignedPartitions = Collections.emptyMap();
+        private Map<Uuid, Set<Integer>> assignedPartitions = Map.of();
 
         public Builder(String memberId) {
             this.memberId = Objects.requireNonNull(memberId);

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/CurrentAssignmentBuilder.java

@@ -18,7 +18,6 @@ package org.apache.kafka.coordinator.group.streams;
 
 import org.apache.kafka.common.errors.FencedMemberEpochException;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
@@ -251,8 +250,8 @@ public class CurrentAssignmentBuilder {
         for (String subtopologyId : allSubtopologyIds) {
             hasUnreleasedTasks |= computeAssignmentDifferenceForOneSubtopology(
                 subtopologyId,
-                currentAssignment.getOrDefault(subtopologyId, Collections.emptySet()),
+                currentAssignment.getOrDefault(subtopologyId, Set.of()),
-                targetAssignment.getOrDefault(subtopologyId, Collections.emptySet()),
+                targetAssignment.getOrDefault(subtopologyId, Set.of()),
                 resultAssignedTasks,
                 resultTasksPendingRevocation,
                 resultTasksPendingAssignment,

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/StreamsCoordinatorRecordHelpers.java

@@ -40,7 +40,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * This class contains helper methods to create records stored in the __consumer_offsets topic.
@@ -72,7 +71,7 @@ public class StreamsCoordinatorRecordHelpers {
                         new StreamsGroupMemberMetadataValue.KeyValue()
                             .setKey(e.getKey())
                             .setValue(e.getValue())
-                    ).sorted(Comparator.comparing(StreamsGroupMemberMetadataValue.KeyValue::key)).collect(Collectors.toList())),
+                    ).sorted(Comparator.comparing(StreamsGroupMemberMetadataValue.KeyValue::key)).toList()),
                 (short) 0
             )
         );
@@ -401,12 +400,12 @@ public class StreamsCoordinatorRecordHelpers {
             List<StreamsGroupTopologyValue.TopicInfo> repartitionSourceTopics =
                 subtopology.repartitionSourceTopics().stream()
                     .map(StreamsCoordinatorRecordHelpers::convertToTopicInfo)
-                    .collect(Collectors.toList());
+                    .toList();
 
             List<StreamsGroupTopologyValue.TopicInfo> stateChangelogTopics =
                 subtopology.stateChangelogTopics().stream()
                     .map(StreamsCoordinatorRecordHelpers::convertToTopicInfo)
-                    .collect(Collectors.toList());
+                    .toList();
 
             List<StreamsGroupTopologyValue.CopartitionGroup> copartitionGroups =
                 subtopology.copartitionGroups().stream()
@@ -415,7 +414,7 @@ public class StreamsCoordinatorRecordHelpers {
                         .setSourceTopicRegex(copartitionGroup.sourceTopicRegex())
                         .setRepartitionSourceTopics(copartitionGroup.repartitionSourceTopics())
                     )
-                    .collect(Collectors.toList());
+                    .toList();
 
             value.subtopologies().add(
                 new StreamsGroupTopologyValue.Subtopology()
@@ -434,7 +433,7 @@ public class StreamsCoordinatorRecordHelpers {
     private static StreamsGroupTopologyValue.TopicInfo convertToTopicInfo(StreamsGroupHeartbeatRequestData.TopicInfo topicInfo) {
         List<StreamsGroupTopologyValue.TopicConfig> topicConfigs = topicInfo.topicConfigs() != null ? topicInfo.topicConfigs().stream()
             .map(config -> new StreamsGroupTopologyValue.TopicConfig().setKey(config.key()).setValue(config.value()))
-            .collect(Collectors.toList()) : null;
+            .toList() : null;
         return new StreamsGroupTopologyValue.TopicInfo()
             .setName(topicInfo.name())
             .setTopicConfigs(topicConfigs)

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/StreamsGroup.java

@@ -511,9 +511,9 @@ public class StreamsGroup implements Group {
     ) {
         Map<Integer, Set<String>> tasks = currentStandbyTaskToProcessIds.get(subtopologyId);
         if (tasks == null) {
-            return Collections.emptySet();
+            return Set.of();
         } else {
-            return tasks.getOrDefault(taskId, Collections.emptySet());
+            return tasks.getOrDefault(taskId, Set.of());
         }
     }
 
@@ -529,9 +529,9 @@ public class StreamsGroup implements Group {
     ) {
         Map<Integer, Set<String>> tasks = currentWarmupTaskToProcessIds.get(subtopologyId);
         if (tasks == null) {
-            return Collections.emptySet();
+            return Set.of();
         } else {
-            return tasks.getOrDefault(taskId, Collections.emptySet());
+            return tasks.getOrDefault(taskId, Set.of());
         }
     }
 

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/StreamsGroupMember.java

@@ -341,7 +341,7 @@ public record StreamsGroupMember(String memberId,
                 entry -> new StreamsGroupDescribeResponseData.KeyValue()
                     .setKey(entry.getKey())
                     .setValue(entry.getValue())
-            ).collect(Collectors.toList()))
+            ).toList())
             .setProcessId(processId)
             .setTopologyEpoch(topologyEpoch)
             .setUserEndpoint(

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/TasksTuple.java

@@ -50,9 +50,9 @@ public record TasksTuple(Map<String, Set<Integer>> activeTasks,
      * An empty task tuple.
      */
     public static final TasksTuple EMPTY = new TasksTuple(
-        Collections.emptyMap(),
+        Map.of(),
-        Collections.emptyMap(),
+        Map.of(),
-        Collections.emptyMap()
+        Map.of()
     );
 
     /**

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/MemberAssignment.java

@@ -16,7 +16,6 @@
  */
 package org.apache.kafka.coordinator.group.streams.assignor;
 
-import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -37,6 +36,6 @@ public record MemberAssignment(Map<String, Set<Integer>> activeTasks,
     }
 
     public static MemberAssignment empty() {
-        return new MemberAssignment(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap());
+        return new MemberAssignment(Map.of(), Map.of(), Map.of());
     }
 }

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredInternalTopic.java

@@ -23,7 +23,6 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
-import java.util.stream.Collectors;
 
 /**
  * Captures the properties required for configuring the internal topics we create for changelogs and repartitioning etc.
@@ -57,12 +56,11 @@ public record ConfiguredInternalTopic(String name,
             .setPartitions(numberOfPartitions)
             .setReplicationFactor(replicationFactor.orElse((short) 0))
             .setTopicConfigs(
-                topicConfigs != null ?
+                topicConfigs.entrySet().stream().map(
-                    topicConfigs.entrySet().stream().map(
+                    y -> new StreamsGroupDescribeResponseData.KeyValue()
-                        y -> new StreamsGroupDescribeResponseData.KeyValue()
+                        .setKey(y.getKey())
-                            .setKey(y.getKey())
+                        .setValue(y.getValue())
-                            .setValue(y.getValue())
+                ).toList()
-                    ).collect(Collectors.toList()) : null
             );
     }
 

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredSubtopology.java

@@ -21,7 +21,6 @@ import org.apache.kafka.common.message.StreamsGroupDescribeResponseData;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * Internal representation of a subtopology.
@@ -51,12 +50,12 @@ public record ConfiguredSubtopology(Set<String> sourceTopics,
     public StreamsGroupDescribeResponseData.Subtopology asStreamsGroupDescribeSubtopology(String subtopologyId) {
         return new StreamsGroupDescribeResponseData.Subtopology()
             .setSubtopologyId(subtopologyId)
-            .setSourceTopics(sourceTopics.stream().sorted().collect(Collectors.toList()))
+            .setSourceTopics(sourceTopics.stream().sorted().toList())
-            .setRepartitionSinkTopics(repartitionSinkTopics.stream().sorted().collect(Collectors.toList()))
+            .setRepartitionSinkTopics(repartitionSinkTopics.stream().sorted().toList())
             .setRepartitionSourceTopics(repartitionSourceTopics.values().stream()
-                .map(ConfiguredInternalTopic::asStreamsGroupDescribeTopicInfo).sorted().collect(Collectors.toList()))
+                .map(ConfiguredInternalTopic::asStreamsGroupDescribeTopicInfo).sorted().toList())
             .setStateChangelogTopics(stateChangelogTopics.values().stream()
-                .map(ConfiguredInternalTopic::asStreamsGroupDescribeTopicInfo).sorted().collect(Collectors.toList()));
+                .map(ConfiguredInternalTopic::asStreamsGroupDescribeTopicInfo).sorted().toList());
     }
 
 }

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredTopology.java

@@ -19,12 +19,11 @@ package org.apache.kafka.coordinator.group.streams.topics;
 import org.apache.kafka.common.message.CreateTopicsRequestData.CreatableTopic;
 import org.apache.kafka.common.message.StreamsGroupDescribeResponseData;
 
-import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.SortedMap;
-import java.util.stream.Collectors;
 
 /**
  * This class captures the result of taking a topology definition sent by the client and using the current state of the topics inside the
@@ -68,7 +67,7 @@ public record ConfiguredTopology(int topologyEpoch,
             .setSubtopologies(
                 subtopologies.map(stringConfiguredSubtopologyMap -> stringConfiguredSubtopologyMap.entrySet().stream().map(
                     entry -> entry.getValue().asStreamsGroupDescribeSubtopology(entry.getKey())
-                ).collect(Collectors.toList())).orElse(Collections.emptyList())
+                ).toList()).orElse(List.of())
             );
     }
 

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/topics/CopartitionedTopicsEnforcer.java

@@ -22,7 +22,6 @@ import org.apache.kafka.common.utils.LogContext;
 import org.slf4j.Logger;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -74,7 +73,7 @@ public class CopartitionedTopicsEnforcer {
                                         final Set<String> flexibleRepartitionTopics) throws StreamsInvalidTopologyException {
         if (copartitionedTopics.isEmpty()) {
             log.debug("Ignoring unexpected empty copartitioned topics set.");
-            return Collections.emptyMap();
+            return Map.of();
         }
         final Map<String, Integer> returnedPartitionCounts = new HashMap<>();
 

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/topics/InternalTopicManager.java

@@ -27,7 +27,6 @@ import org.apache.kafka.coordinator.group.streams.TopicMetadata;
 import org.slf4j.Logger;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
@@ -290,7 +289,7 @@ public class InternalTopicManager {
             topicInfo.topicConfigs() != null ? topicInfo.topicConfigs().stream()
                 .collect(Collectors.toMap(StreamsGroupTopologyValue.TopicConfig::key,
                     StreamsGroupTopologyValue.TopicConfig::value))
-                : Collections.emptyMap()
+                : Map.of()
         );
     }
 
@@ -304,6 +303,6 @@ public class InternalTopicManager {
                 copartitionGroup.repartitionSourceTopics().stream()
                     .map(i -> subtopology.repartitionSourceTopics().get(i).name())
             ).collect(Collectors.toSet())
-        ).collect(Collectors.toList());
+        ).toList();
     }
 }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/Assertions.java

@@ -41,7 +41,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Consumer;
-import java.util.stream.Collectors;
 
 import static org.junit.jupiter.api.AssertionFailureBuilder.assertionFailure;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -115,12 +114,12 @@ public class Assertions {
                     slice
                         .stream()
                         .sorted(Comparator.comparing(Object::toString))
-                        .collect(Collectors.toList()),
+                        .toList(),
                     actualRecords
                         .subList(j, j + slice.size())
                         .stream()
                         .sorted(Comparator.comparing(Object::toString))
-                        .collect(Collectors.toList())
+                        .toList()
                 );
 
                 j += slice.size();

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupCoordinatorConfigTest.java

@@ -34,7 +34,6 @@ import org.apache.kafka.coordinator.group.assignor.UniformAssignor;
 import org.junit.jupiter.api.Test;
 
 import java.time.Duration;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -144,7 +143,7 @@ public class GroupCoordinatorConfigTest {
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_SESSION_TIMEOUT_MS_CONFIG, 555);
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_HEARTBEAT_INTERVAL_MS_CONFIG, 200);
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_MAX_SIZE_CONFIG, 55);
-        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, Collections.singletonList(RangeAssignor.class));
+        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, List.of(RangeAssignor.class));
         configs.put(GroupCoordinatorConfig.OFFSETS_TOPIC_SEGMENT_BYTES_CONFIG, 2222);
         configs.put(GroupCoordinatorConfig.OFFSET_METADATA_MAX_SIZE_CONFIG, 3333);
         configs.put(GroupCoordinatorConfig.GROUP_MAX_SIZE_CONFIG, 60);
@@ -243,7 +242,7 @@ public class GroupCoordinatorConfigTest {
                 assertThrows(ConfigException.class, () -> createConfig(configs)).getMessage());
 
         configs.clear();
-        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, Collections.singletonList(Object.class));
+        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, List.of(Object.class));
         assertEquals("class java.lang.Object is not an instance of org.apache.kafka.coordinator.group.api.assignor.ConsumerGroupPartitionAssignor",
                 assertThrows(KafkaException.class, () -> createConfig(configs)).getMessage());
 
@@ -297,7 +296,7 @@ public class GroupCoordinatorConfigTest {
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_HEARTBEAT_INTERVAL_MS_CONFIG, 5);
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_MIN_HEARTBEAT_INTERVAL_MS_CONFIG, 5);
         configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_MAX_SIZE_CONFIG, Integer.MAX_VALUE);
-        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, Collections.singletonList(RangeAssignor.class));
+        configs.put(GroupCoordinatorConfig.CONSUMER_GROUP_ASSIGNORS_CONFIG, List.of(RangeAssignor.class));
         configs.put(GroupCoordinatorConfig.OFFSETS_TOPIC_SEGMENT_BYTES_CONFIG, 1000);
         configs.put(GroupCoordinatorConfig.OFFSET_METADATA_MAX_SIZE_CONFIG, offsetMetadataMaxSize);
         configs.put(GroupCoordinatorConfig.GROUP_MAX_SIZE_CONFIG, Integer.MAX_VALUE);

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupCoordinatorRecordHelpersTest.java

@@ -55,7 +55,6 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -570,7 +569,7 @@ public class GroupCoordinatorRecordHelpersTest {
         assertThrows(IllegalStateException.class, () ->
             GroupCoordinatorRecordHelpers.newGroupMetadataRecord(
                 group,
-                Collections.emptyMap()
+                Map.of()
             ));
     }
 
@@ -620,7 +619,7 @@ public class GroupCoordinatorRecordHelpersTest {
         assertThrows(IllegalStateException.class, () ->
             GroupCoordinatorRecordHelpers.newGroupMetadataRecord(
                 group,
-                Collections.emptyMap()
+                Map.of()
             ));
     }
       
@@ -628,7 +627,7 @@ public class GroupCoordinatorRecordHelpersTest {
     public void testEmptyGroupMetadataRecord() {
         Time time = new MockTime();
 
-        List<GroupMetadataValue.MemberMetadata> expectedMembers = Collections.emptyList();
+        List<GroupMetadataValue.MemberMetadata> expectedMembers = List.of();
 
         CoordinatorRecord expectedRecord = CoordinatorRecord.record(
             new GroupMetadataKey()

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupCoordinatorServiceTest.java

@@ -113,7 +113,6 @@ import org.mockito.ArgumentMatchers;
 import java.net.InetAddress;
 import java.time.Duration;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.OptionalInt;
@@ -289,7 +288,7 @@ public class GroupCoordinatorServiceTest {
         assertEquals(
             new StreamsGroupHeartbeatResult(
                 new StreamsGroupHeartbeatResponseData().setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code()),
-                Collections.emptyMap()
+                Map.of()
             ),
             future.get()
         );
@@ -314,7 +313,7 @@ public class GroupCoordinatorServiceTest {
         )).thenReturn(CompletableFuture.completedFuture(
             new StreamsGroupHeartbeatResult(
                 new StreamsGroupHeartbeatResponseData(),
-                Collections.emptyMap()
+                Map.of()
             )
         ));
 
@@ -323,7 +322,7 @@ public class GroupCoordinatorServiceTest {
             request
         );
 
-        assertEquals(new StreamsGroupHeartbeatResult(new StreamsGroupHeartbeatResponseData(), Collections.emptyMap()), future.get(5, TimeUnit.SECONDS));
+        assertEquals(new StreamsGroupHeartbeatResult(new StreamsGroupHeartbeatResponseData(), Map.of()), future.get(5, TimeUnit.SECONDS));
     }
 
     private static Stream<Arguments> testStreamsGroupHeartbeatWithExceptionSource() {
@@ -376,7 +375,7 @@ public class GroupCoordinatorServiceTest {
                 new StreamsGroupHeartbeatResponseData()
                     .setErrorCode(expectedErrorCode)
                     .setErrorMessage(expectedErrorMessage),
-                Collections.emptyMap()
+                Map.of()
             ),
             future.get(5, TimeUnit.SECONDS)
         );
@@ -880,9 +879,9 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("list-groups"),
             ArgumentMatchers.any()
         )).thenReturn(Arrays.asList(
-            CompletableFuture.completedFuture(Collections.singletonList(expectedResults.get(0))),
+            CompletableFuture.completedFuture(List.of(expectedResults.get(0))),
-            CompletableFuture.completedFuture(Collections.singletonList(expectedResults.get(1))),
+            CompletableFuture.completedFuture(List.of(expectedResults.get(1))),
-            CompletableFuture.completedFuture(Collections.singletonList(expectedResults.get(2)))
+            CompletableFuture.completedFuture(List.of(expectedResults.get(2)))
         ));
 
         CompletableFuture<ListGroupsResponseData> responseFuture = service.listGroups(
@@ -920,8 +919,8 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("list-groups"),
             ArgumentMatchers.any()
         )).thenReturn(Arrays.asList(
-            CompletableFuture.completedFuture(Collections.singletonList(expectedResults.get(0))),
+            CompletableFuture.completedFuture(List.of(expectedResults.get(0))),
-            CompletableFuture.completedFuture(Collections.singletonList(expectedResults.get(1))),
+            CompletableFuture.completedFuture(List.of(expectedResults.get(1))),
             FutureUtils.failedFuture(new NotCoordinatorException(""))
         ));
 
@@ -947,8 +946,8 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("list-groups"),
             ArgumentMatchers.any()
         )).thenReturn(Arrays.asList(
-            CompletableFuture.completedFuture(Collections.emptyList()),
+            CompletableFuture.completedFuture(List.of()),
-            CompletableFuture.completedFuture(Collections.emptyList()),
+            CompletableFuture.completedFuture(List.of()),
             FutureUtils.failedFuture(new CoordinatorLoadInProgressException(""))
         ));
 
@@ -1033,7 +1032,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("describe-groups"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup1)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup1)));
 
         CompletableFuture<Object> describedGroupFuture = new CompletableFuture<>();
         when(runtime.scheduleReadOperation(
@@ -1046,7 +1045,7 @@ public class GroupCoordinatorServiceTest {
             service.describeGroups(requestContext(ApiKeys.DESCRIBE_GROUPS), Arrays.asList("group-id-1", "group-id-2"));
 
         assertFalse(future.isDone());
-        describedGroupFuture.complete(Collections.singletonList(describedGroup2));
+        describedGroupFuture.complete(List.of(describedGroup2));
         assertEquals(expectedDescribedGroups, future.get());
     }
 
@@ -1074,7 +1073,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("describe-groups"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup)));
 
         CompletableFuture<List<DescribeGroupsResponseData.DescribedGroup>> future =
             service.describeGroups(requestContext(ApiKeys.DESCRIBE_GROUPS), Arrays.asList("", null));
@@ -1102,10 +1101,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<DescribeGroupsResponseData.DescribedGroup>> future =
-            service.describeGroups(requestContext(ApiKeys.DESCRIBE_GROUPS), Collections.singletonList("group-id"));
+            service.describeGroups(requestContext(ApiKeys.DESCRIBE_GROUPS), List.of("group-id"));
 
         assertEquals(
-            Collections.singletonList(new DescribeGroupsResponseData.DescribedGroup()
+            List.of(new DescribeGroupsResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_LOAD_IN_PROGRESS.code())
             ),
@@ -1123,11 +1122,11 @@ public class GroupCoordinatorServiceTest {
 
         CompletableFuture<List<DescribeGroupsResponseData.DescribedGroup>> future = service.describeGroups(
             requestContext(ApiKeys.DESCRIBE_GROUPS),
-            Collections.singletonList("group-id")
+            List.of("group-id")
         );
 
         assertEquals(
-            Collections.singletonList(new DescribeGroupsResponseData.DescribedGroup()
+            List.of(new DescribeGroupsResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code())
             ),
@@ -1157,17 +1156,17 @@ public class GroupCoordinatorServiceTest {
                 .setGroupId("group");
         if (!fetchAllOffsets) {
             request
-                .setTopics(Collections.singletonList(new OffsetFetchRequestData.OffsetFetchRequestTopics()
+                .setTopics(List.of(new OffsetFetchRequestData.OffsetFetchRequestTopics()
                     .setName("foo")
-                    .setPartitionIndexes(Collections.singletonList(0))));
+                    .setPartitionIndexes(List.of(0))));
         }
 
         OffsetFetchResponseData.OffsetFetchResponseGroup response =
             new OffsetFetchResponseData.OffsetFetchResponseGroup()
                 .setGroupId("group")
-                .setTopics(Collections.singletonList(new OffsetFetchResponseData.OffsetFetchResponseTopics()
+                .setTopics(List.of(new OffsetFetchResponseData.OffsetFetchResponseTopics()
                     .setName("foo")
-                    .setPartitions(Collections.singletonList(new OffsetFetchResponseData.OffsetFetchResponsePartitions()
+                    .setPartitions(List.of(new OffsetFetchResponseData.OffsetFetchResponsePartitions()
                         .setPartitionIndex(0)
                         .setCommittedOffset(100L)))));
 
@@ -1219,9 +1218,9 @@ public class GroupCoordinatorServiceTest {
                 .setGroupId("group");
         if (!fetchAllOffsets) {
             request
-                .setTopics(Collections.singletonList(new OffsetFetchRequestData.OffsetFetchRequestTopics()
+                .setTopics(List.of(new OffsetFetchRequestData.OffsetFetchRequestTopics()
                     .setName("foo")
-                    .setPartitionIndexes(Collections.singletonList(0))));
+                    .setPartitionIndexes(List.of(0))));
         }
 
         TriFunction<RequestContext, OffsetFetchRequestData.OffsetFetchRequestGroup, Boolean, CompletableFuture<OffsetFetchResponseData.OffsetFetchResponseGroup>> fetchOffsets =
@@ -1269,9 +1268,9 @@ public class GroupCoordinatorServiceTest {
                 .setGroupId("group");
         if (!fetchAllOffsets) {
             request
-                .setTopics(Collections.singletonList(new OffsetFetchRequestData.OffsetFetchRequestTopics()
+                .setTopics(List.of(new OffsetFetchRequestData.OffsetFetchRequestTopics()
                     .setName("foo")
-                    .setPartitionIndexes(Collections.singletonList(0))));
+                    .setPartitionIndexes(List.of(0))));
         }
 
         when(runtime.scheduleWriteOperation(
@@ -1422,7 +1421,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("consumer-group-describe"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup1)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup1)));
 
         CompletableFuture<Object> describedGroupFuture = new CompletableFuture<>();
         when(runtime.scheduleReadOperation(
@@ -1435,7 +1434,7 @@ public class GroupCoordinatorServiceTest {
             service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), Arrays.asList("group-id-1", "group-id-2"));
 
         assertFalse(future.isDone());
-        describedGroupFuture.complete(Collections.singletonList(describedGroup2));
+        describedGroupFuture.complete(List.of(describedGroup2));
         assertEquals(expectedDescribedGroups, future.get());
     }
 
@@ -1463,7 +1462,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("consumer-group-describe"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup)));
 
         CompletableFuture<List<ConsumerGroupDescribeResponseData.DescribedGroup>> future =
             service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), Arrays.asList("", null));
@@ -1490,10 +1489,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<ConsumerGroupDescribeResponseData.DescribedGroup>> future =
-            service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), Collections.singletonList("group-id"));
+            service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), List.of("group-id"));
 
         assertEquals(
-            Collections.singletonList(new ConsumerGroupDescribeResponseData.DescribedGroup()
+            List.of(new ConsumerGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_LOAD_IN_PROGRESS.code())
             ),
@@ -1517,10 +1516,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<ConsumerGroupDescribeResponseData.DescribedGroup>> future =
-            service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), Collections.singletonList("group-id"));
+            service.consumerGroupDescribe(requestContext(ApiKeys.CONSUMER_GROUP_DESCRIBE), List.of("group-id"));
 
         assertEquals(
-            Collections.singletonList(new ConsumerGroupDescribeResponseData.DescribedGroup()
+            List.of(new ConsumerGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code())
             ),
@@ -1551,7 +1550,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("streams-group-describe"),
             ArgumentMatchers.eq(new TopicPartition("__consumer_offsets", 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup1)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup1)));
 
         CompletableFuture<Object> describedGroupFuture = new CompletableFuture<>();
         when(runtime.scheduleReadOperation(
@@ -1564,7 +1563,7 @@ public class GroupCoordinatorServiceTest {
             service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), Arrays.asList("group-id-1", "group-id-2"));
 
         assertFalse(future.isDone());
-        describedGroupFuture.complete(Collections.singletonList(describedGroup2));
+        describedGroupFuture.complete(List.of(describedGroup2));
         assertEquals(expectedDescribedGroups, future.get());
     }
 
@@ -1592,7 +1591,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("streams-group-describe"),
             ArgumentMatchers.eq(new TopicPartition("__consumer_offsets", 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup)));
 
         CompletableFuture<List<StreamsGroupDescribeResponseData.DescribedGroup>> future =
             service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), Arrays.asList("", null));
@@ -1619,10 +1618,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<StreamsGroupDescribeResponseData.DescribedGroup>> future =
-            service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), Collections.singletonList("group-id"));
+            service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), List.of("group-id"));
 
         assertEquals(
-            Collections.singletonList(new StreamsGroupDescribeResponseData.DescribedGroup()
+            List.of(new StreamsGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_LOAD_IN_PROGRESS.code())
             ),
@@ -1646,10 +1645,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<StreamsGroupDescribeResponseData.DescribedGroup>> future =
-            service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), Collections.singletonList("group-id"));
+            service.streamsGroupDescribe(requestContext(ApiKeys.STREAMS_GROUP_DESCRIBE), List.of("group-id"));
 
         assertEquals(
-            Collections.singletonList(new StreamsGroupDescribeResponseData.DescribedGroup()
+            List.of(new StreamsGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("group-id")
                 .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code())
             ),
@@ -1667,10 +1666,10 @@ public class GroupCoordinatorServiceTest {
             .build(true);
 
         OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection requestTopicCollection =
-            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(Collections.singletonList(
+            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(List.of(
                 new OffsetDeleteRequestData.OffsetDeleteRequestTopic()
                     .setName(TOPIC_NAME)
-                    .setPartitions(Collections.singletonList(
+                    .setPartitions(List.of(
                         new OffsetDeleteRequestData.OffsetDeleteRequestPartition().setPartitionIndex(0)
                     ))
             ).iterator());
@@ -1679,11 +1678,11 @@ public class GroupCoordinatorServiceTest {
             .setTopics(requestTopicCollection);
 
         OffsetDeleteResponseData.OffsetDeleteResponsePartitionCollection responsePartitionCollection =
-            new OffsetDeleteResponseData.OffsetDeleteResponsePartitionCollection(Collections.singletonList(
+            new OffsetDeleteResponseData.OffsetDeleteResponsePartitionCollection(List.of(
                 new OffsetDeleteResponseData.OffsetDeleteResponsePartition().setPartitionIndex(0)
             ).iterator());
         OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection responseTopicCollection =
-            new OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection(Collections.singletonList(
+            new OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection(List.of(
                 new OffsetDeleteResponseData.OffsetDeleteResponseTopic().setPartitions(responsePartitionCollection)
             ).iterator());
         OffsetDeleteResponseData response = new OffsetDeleteResponseData()
@@ -1716,10 +1715,10 @@ public class GroupCoordinatorServiceTest {
             .build(true);
 
         OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection requestTopicCollection =
-            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(Collections.singletonList(
+            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(List.of(
                 new OffsetDeleteRequestData.OffsetDeleteRequestTopic()
                     .setName(TOPIC_NAME)
-                    .setPartitions(Collections.singletonList(
+                    .setPartitions(List.of(
                         new OffsetDeleteRequestData.OffsetDeleteRequestPartition().setPartitionIndex(0)
                     ))
             ).iterator());
@@ -1760,10 +1759,10 @@ public class GroupCoordinatorServiceTest {
             .build(true);
 
         OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection requestTopicCollection =
-            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(Collections.singletonList(
+            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(List.of(
                 new OffsetDeleteRequestData.OffsetDeleteRequestTopic()
                     .setName(TOPIC_NAME)
-                    .setPartitions(Collections.singletonList(
+                    .setPartitions(List.of(
                         new OffsetDeleteRequestData.OffsetDeleteRequestPartition().setPartitionIndex(0)
                     ))
             ).iterator());
@@ -2272,12 +2271,12 @@ public class GroupCoordinatorServiceTest {
         CompletableFuture<DeleteGroupsResponseData.DeletableGroupResultCollection> future =
             service.deleteGroups(
                 requestContext(ApiKeys.DELETE_GROUPS),
-                Collections.singletonList("group-id"),
+                List.of("group-id"),
                 BufferSupplier.NO_CACHING
             );
 
         assertEquals(
-            new DeleteGroupsResponseData.DeletableGroupResultCollection(Collections.singletonList(
+            new DeleteGroupsResponseData.DeletableGroupResultCollection(List.of(
                 new DeleteGroupsResponseData.DeletableGroupResult()
                     .setGroupId("group-id")
                     .setErrorCode(expectedErrorCode)
@@ -2297,13 +2296,13 @@ public class GroupCoordinatorServiceTest {
 
         CompletableFuture<DeleteGroupsResponseData.DeletableGroupResultCollection> future = service.deleteGroups(
             requestContext(ApiKeys.DELETE_GROUPS),
-            Collections.singletonList("foo"),
+            List.of("foo"),
             BufferSupplier.NO_CACHING
         );
 
         assertEquals(
             new DeleteGroupsResponseData.DeletableGroupResultCollection(
-                Collections.singletonList(new DeleteGroupsResponseData.DeletableGroupResult()
+                List.of(new DeleteGroupsResponseData.DeletableGroupResult()
                     .setGroupId("foo")
                     .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code())
                 ).iterator()
@@ -2325,9 +2324,9 @@ public class GroupCoordinatorServiceTest {
             .setTransactionalId("transactional-id")
             .setMemberId("member-id")
             .setGenerationId(10)
-            .setTopics(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
+            .setTopics(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
+                .setPartitions(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                     .setPartitionIndex(0)
                     .setCommittedOffset(100)))));
 
@@ -2339,9 +2338,9 @@ public class GroupCoordinatorServiceTest {
 
         assertEquals(
             new TxnOffsetCommitResponseData()
-                .setTopics(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
+                .setTopics(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                     .setName(TOPIC_NAME)
-                    .setPartitions(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
+                    .setPartitions(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                         .setPartitionIndex(0)
                         .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code()))))),
             future.get()
@@ -2363,9 +2362,9 @@ public class GroupCoordinatorServiceTest {
             .setTransactionalId("transactional-id")
             .setMemberId("member-id")
             .setGenerationId(10)
-            .setTopics(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
+            .setTopics(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
+                .setPartitions(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                     .setPartitionIndex(0)
                     .setCommittedOffset(100)))));
 
@@ -2377,9 +2376,9 @@ public class GroupCoordinatorServiceTest {
 
         assertEquals(
             new TxnOffsetCommitResponseData()
-                .setTopics(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
+                .setTopics(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                     .setName(TOPIC_NAME)
-                    .setPartitions(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
+                    .setPartitions(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                         .setPartitionIndex(0)
                         .setErrorCode(Errors.INVALID_GROUP_ID.code()))))),
             future.get()
@@ -2402,16 +2401,16 @@ public class GroupCoordinatorServiceTest {
             .setProducerEpoch((short) 5)
             .setMemberId("member-id")
             .setGenerationId(10)
-            .setTopics(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
+            .setTopics(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
+                .setPartitions(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                     .setPartitionIndex(0)
                     .setCommittedOffset(100)))));
 
         TxnOffsetCommitResponseData response = new TxnOffsetCommitResponseData()
-            .setTopics(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
+            .setTopics(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
+                .setPartitions(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                     .setPartitionIndex(0)
                     .setErrorCode(Errors.NONE.code())))));
 
@@ -2457,16 +2456,16 @@ public class GroupCoordinatorServiceTest {
             .setProducerEpoch((short) 5)
             .setMemberId("member-id")
             .setGenerationId(10)
-            .setTopics(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
+            .setTopics(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
+                .setPartitions(List.of(new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                     .setPartitionIndex(0)
                     .setCommittedOffset(100)))));
 
         TxnOffsetCommitResponseData response = new TxnOffsetCommitResponseData()
-            .setTopics(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
+            .setTopics(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                 .setName(TOPIC_NAME)
-                .setPartitions(Collections.singletonList(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
+                .setPartitions(List.of(new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                     .setPartitionIndex(0)
                     .setErrorCode(expectedError.code())))));
 
@@ -2582,7 +2581,7 @@ public class GroupCoordinatorServiceTest {
         // The exception is logged and swallowed.
         assertDoesNotThrow(() ->
             service.onPartitionsDeleted(
-                Collections.singletonList(new TopicPartition("foo", 0)),
+                List.of(new TopicPartition("foo", 0)),
                 BufferSupplier.NO_CACHING
             )
         );
@@ -2597,7 +2596,7 @@ public class GroupCoordinatorServiceTest {
             .build();
 
         assertThrows(CoordinatorNotAvailableException.class, () -> service.onPartitionsDeleted(
-            Collections.singletonList(new TopicPartition("foo", 0)),
+            List.of(new TopicPartition("foo", 0)),
             BufferSupplier.NO_CACHING
         ));
     }
@@ -2708,7 +2707,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("share-group-describe"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup1)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup1)));
 
         CompletableFuture<Object> describedGroupFuture = new CompletableFuture<>();
         when(runtime.scheduleReadOperation(
@@ -2721,7 +2720,7 @@ public class GroupCoordinatorServiceTest {
             service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), Arrays.asList("share-group-id-1", "share-group-id-2"));
 
         assertFalse(future.isDone());
-        describedGroupFuture.complete(Collections.singletonList(describedGroup2));
+        describedGroupFuture.complete(List.of(describedGroup2));
         assertEquals(expectedDescribedGroups, future.get());
     }
 
@@ -2749,7 +2748,7 @@ public class GroupCoordinatorServiceTest {
             ArgumentMatchers.eq("share-group-describe"),
             ArgumentMatchers.eq(new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)),
             ArgumentMatchers.any()
-        )).thenReturn(CompletableFuture.completedFuture(Collections.singletonList(describedGroup)));
+        )).thenReturn(CompletableFuture.completedFuture(List.of(describedGroup)));
 
         CompletableFuture<List<ShareGroupDescribeResponseData.DescribedGroup>> future =
             service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), Arrays.asList("", null));
@@ -2776,10 +2775,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<ShareGroupDescribeResponseData.DescribedGroup>> future =
-            service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), Collections.singletonList("share-group-id"));
+            service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), List.of("share-group-id"));
 
         assertEquals(
-            Collections.singletonList(new ShareGroupDescribeResponseData.DescribedGroup()
+            List.of(new ShareGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("share-group-id")
                 .setErrorCode(Errors.COORDINATOR_LOAD_IN_PROGRESS.code())
             ),
@@ -2803,10 +2802,10 @@ public class GroupCoordinatorServiceTest {
         ));
 
         CompletableFuture<List<ShareGroupDescribeResponseData.DescribedGroup>> future =
-            service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), Collections.singletonList("share-group-id"));
+            service.shareGroupDescribe(requestContext(ApiKeys.SHARE_GROUP_DESCRIBE), List.of("share-group-id"));
 
         assertEquals(
-            Collections.singletonList(new ShareGroupDescribeResponseData.DescribedGroup()
+            List.of(new ShareGroupDescribeResponseData.DescribedGroup()
                 .setGroupId("share-group-id")
                 .setErrorCode(Errors.COORDINATOR_NOT_AVAILABLE.code())
             ),

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupCoordinatorShardTest.java

@@ -102,7 +102,6 @@ import org.mockito.Mockito;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -151,7 +150,7 @@ public class GroupCoordinatorShardTest {
         RequestContext context = requestContext(ApiKeys.CONSUMER_GROUP_HEARTBEAT);
         ConsumerGroupHeartbeatRequestData request = new ConsumerGroupHeartbeatRequestData();
         CoordinatorResult<ConsumerGroupHeartbeatResponseData, CoordinatorRecord> result = new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
             new ConsumerGroupHeartbeatResponseData()
         );
 
@@ -183,8 +182,8 @@ public class GroupCoordinatorShardTest {
         RequestContext context = requestContext(ApiKeys.STREAMS_GROUP_HEARTBEAT);
         StreamsGroupHeartbeatRequestData request = new StreamsGroupHeartbeatRequestData();
         CoordinatorResult<StreamsGroupHeartbeatResult, CoordinatorRecord> result = new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
-            new StreamsGroupHeartbeatResult(new StreamsGroupHeartbeatResponseData(), Collections.emptyMap())
+            new StreamsGroupHeartbeatResult(new StreamsGroupHeartbeatResponseData(), Map.of())
         );
 
         when(groupMetadataManager.streamsGroupHeartbeat(
@@ -215,7 +214,7 @@ public class GroupCoordinatorShardTest {
         RequestContext context = requestContext(ApiKeys.OFFSET_COMMIT);
         OffsetCommitRequestData request = new OffsetCommitRequestData();
         CoordinatorResult<OffsetCommitResponseData, CoordinatorRecord> result = new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
             new OffsetCommitResponseData()
         );
 
@@ -247,7 +246,7 @@ public class GroupCoordinatorShardTest {
         RequestContext context = requestContext(ApiKeys.TXN_OFFSET_COMMIT);
         TxnOffsetCommitRequestData request = new TxnOffsetCommitRequestData();
         CoordinatorResult<TxnOffsetCommitResponseData, CoordinatorRecord> result = new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
             new TxnOffsetCommitResponseData()
         );
 
@@ -1440,7 +1439,7 @@ public class GroupCoordinatorShardTest {
                 records.add(offsetCommitTombstone);
                 return true;
             });
-        when(offsetMetadataManager.cleanupExpiredOffsets("other-group-id", Collections.emptyList())).thenReturn(false);
+        when(offsetMetadataManager.cleanupExpiredOffsets("other-group-id", List.of())).thenReturn(false);
         doAnswer(invocation -> {
             List<CoordinatorRecord> records = recordsCapture.getValue();
             records.add(groupMetadataTombstone);
@@ -1551,18 +1550,18 @@ public class GroupCoordinatorShardTest {
             metricsShard
         );
 
-        List<CoordinatorRecord> records = Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord(
+        List<CoordinatorRecord> records = List.of(GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord(
             "group",
             "foo",
             0
         ));
 
         when(offsetMetadataManager.onPartitionsDeleted(
-            Collections.singletonList(new TopicPartition("foo", 0))
+            List.of(new TopicPartition("foo", 0))
         )).thenReturn(records);
 
         CoordinatorResult<Void, CoordinatorRecord> result = coordinator.onPartitionsDeleted(
-            Collections.singletonList(new TopicPartition("foo", 0))
+            List.of(new TopicPartition("foo", 0))
         );
 
         assertEquals(records, result.records());
@@ -1611,7 +1610,7 @@ public class GroupCoordinatorShardTest {
         RequestContext context = requestContext(ApiKeys.SHARE_GROUP_HEARTBEAT);
         ShareGroupHeartbeatRequestData request = new ShareGroupHeartbeatRequestData();
         CoordinatorResult<ShareGroupHeartbeatResponseData, CoordinatorRecord> result = new CoordinatorResult<>(
-            Collections.emptyList(),
+            List.of(),
             new ShareGroupHeartbeatResponseData()
         );
 

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/GroupMetadataManagerTestContext.java

@@ -406,7 +406,7 @@ public class GroupMetadataManagerTestContext {
         String protocolType = "consumer";
         String protocolName = "range";
         int generationId = 0;
-        List<SyncGroupRequestData.SyncGroupRequestAssignment> assignment = Collections.emptyList();
+        List<SyncGroupRequestData.SyncGroupRequestAssignment> assignment = List.of();
 
         SyncGroupRequestBuilder withGroupId(String groupId) {
             this.groupId = groupId;
@@ -1131,7 +1131,7 @@ public class GroupMetadataManagerTestContext {
         SyncResult followerSyncResult = sendClassicGroupSync(
             syncRequest.setGroupInstanceId(followerInstanceId)
                        .setMemberId(followerId)
-                       .setAssignments(Collections.emptyList())
+                       .setAssignments(List.of())
         );
 
         assertTrue(followerSyncResult.records.isEmpty());
@@ -1273,7 +1273,7 @@ public class GroupMetadataManagerTestContext {
         List<CoordinatorRecord> expectedRecords = List.of(newGroupMetadataRecord(
             group.groupId(),
             new GroupMetadataValue()
-                .setMembers(Collections.emptyList())
+                .setMembers(List.of())
                 .setGeneration(group.generationId())
                 .setLeader(null)
                 .setProtocolType("consumer")
@@ -1498,10 +1498,10 @@ public class GroupMetadataManagerTestContext {
 
     public void verifyDescribeGroupsBeforeV6ReturnsDeadGroup(String groupId) {
         List<DescribeGroupsResponseData.DescribedGroup> describedGroups =
-            describeGroups(Collections.singletonList(groupId), (short) 5);
+            describeGroups(List.of(groupId), (short) 5);
 
         assertEquals(
-            Collections.singletonList(new DescribeGroupsResponseData.DescribedGroup()
+            List.of(new DescribeGroupsResponseData.DescribedGroup()
                 .setGroupId(groupId)
                 .setGroupState(DEAD.toString())
             ),
@@ -1527,7 +1527,7 @@ public class GroupMetadataManagerTestContext {
                 .withProtocolType(protocolType)
                 .build()
         );
-        assertEquals(Collections.emptyList(), syncResult.records);
+        assertEquals(List.of(), syncResult.records);
         assertFalse(syncResult.syncFuture.isDone());
 
         // Simulate a successful write to log.

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/OffsetMetadataManagerTest.java

@@ -73,12 +73,13 @@ import java.net.InetAddress;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.OptionalLong;
+import java.util.Set;
 
 import static org.apache.kafka.common.requests.OffsetFetchResponse.INVALID_OFFSET;
 import static org.apache.kafka.coordinator.group.metrics.GroupCoordinatorMetrics.OFFSET_COMMITS_SENSOR_NAME;
@@ -140,7 +141,7 @@ public class OffsetMetadataManagerTest {
                         .withMetadataImage(metadataImage)
                         .withGroupCoordinatorMetricsShard(metrics)
                         .withGroupConfigManager(configManager)
-                        .withConfig(GroupCoordinatorConfig.fromProps(Collections.emptyMap()))
+                        .withConfig(GroupCoordinatorConfig.fromProps(Map.of()))
                         .build();
                 }
 
@@ -529,10 +530,10 @@ public class OffsetMetadataManagerTest {
             Errors expectedError
         ) {
             final OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection requestTopicCollection =
-                new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(Collections.singletonList(
+                new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(List.of(
                     new OffsetDeleteRequestData.OffsetDeleteRequestTopic()
                         .setName(topic)
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetDeleteRequestData.OffsetDeleteRequestPartition().setPartitionIndex(partition)
                         ))
                 ).iterator());
@@ -546,15 +547,15 @@ public class OffsetMetadataManagerTest {
             );
 
             final OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection expectedResponseTopicCollection =
-                new OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection(Collections.singletonList(
+                new OffsetDeleteResponseData.OffsetDeleteResponseTopicCollection(List.of(
                     new OffsetDeleteResponseData.OffsetDeleteResponseTopic()
                         .setName(topic)
                         .setPartitions(expectedResponsePartitionCollection)
                 ).iterator());
 
-            List<CoordinatorRecord> expectedRecords = Collections.emptyList();
+            List<CoordinatorRecord> expectedRecords = List.of();
             if (hasOffset(groupId, topic, partition) && expectedError == Errors.NONE) {
-                expectedRecords = Collections.singletonList(
+                expectedRecords = List.of(
                     GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord(groupId, topic, partition)
                 );
             }
@@ -598,10 +599,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -628,10 +629,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -657,10 +658,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -694,10 +695,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -727,10 +728,10 @@ public class OffsetMetadataManagerTest {
                 .setMemberId("member")
                 .setGroupInstanceId("instanceid")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -760,10 +761,10 @@ public class OffsetMetadataManagerTest {
                 .setMemberId("member")
                 .setGroupInstanceId("old-instance-id")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -797,10 +798,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(1)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -832,10 +833,10 @@ public class OffsetMetadataManagerTest {
         assertThrows(UnknownMemberIdException.class, () -> context.commitOffset(
             new OffsetCommitRequestData()
                 .setGroupId("foo")
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -870,10 +871,10 @@ public class OffsetMetadataManagerTest {
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(1)
                 .setRetentionTimeMs(1234L)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -883,10 +884,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitResponseData.OffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -896,7 +897,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -938,7 +939,7 @@ public class OffsetMetadataManagerTest {
 
         // Advance time by half of the session timeout. No timeouts are
         // expired.
-        assertEquals(Collections.emptyList(), context.sleep(5000 / 2));
+        assertEquals(List.of(), context.sleep(5000 / 2));
 
         // Commit.
         context.commitOffset(
@@ -947,10 +948,10 @@ public class OffsetMetadataManagerTest {
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(1)
                 .setRetentionTimeMs(1234L)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -960,7 +961,7 @@ public class OffsetMetadataManagerTest {
 
         // Advance time by half of the session timeout. No timeouts are
         // expired.
-        assertEquals(Collections.emptyList(), context.sleep(5000 / 2));
+        assertEquals(List.of(), context.sleep(5000 / 2));
 
         // Advance time by half of the session timeout again. The timeout should
         // expire and the member is removed from the group.
@@ -977,10 +978,10 @@ public class OffsetMetadataManagerTest {
         CoordinatorResult<OffsetCommitResponseData, CoordinatorRecord> result = context.commitOffset(
             new OffsetCommitRequestData()
                 .setGroupId("foo")
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -990,10 +991,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitResponseData.OffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1003,7 +1004,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1036,10 +1037,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 // Instance id should be ignored.
                 .setGroupInstanceId("instance-id")
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1049,10 +1050,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitResponseData.OffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1062,7 +1063,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1094,10 +1095,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1128,10 +1129,10 @@ public class OffsetMetadataManagerTest {
             .setGroupId("foo")
             .setMemberId("member")
             .setGenerationIdOrMemberEpoch(9)
-            .setTopics(Collections.singletonList(
+            .setTopics(List.of(
                 new OffsetCommitRequestData.OffsetCommitRequestTopic()
                     .setName("bar")
-                    .setPartitions(Collections.singletonList(
+                    .setPartitions(List.of(
                         new OffsetCommitRequestData.OffsetCommitRequestPartition()
                             .setPartitionIndex(0)
                             .setCommittedOffset(100L)
@@ -1168,10 +1169,10 @@ public class OffsetMetadataManagerTest {
             .setGroupId("foo")
             .setMemberId("member")
             .setGenerationIdOrMemberEpoch(9)
-            .setTopics(Collections.singletonList(
+            .setTopics(List.of(
                 new OffsetCommitRequestData.OffsetCommitRequestTopic()
                     .setName("bar")
-                    .setPartitions(Collections.singletonList(
+                    .setPartitions(List.of(
                         new OffsetCommitRequestData.OffsetCommitRequestPartition()
                             .setPartitionIndex(0)
                             .setCommittedOffset(100L)
@@ -1199,10 +1200,10 @@ public class OffsetMetadataManagerTest {
         CoordinatorResult<OffsetCommitResponseData, CoordinatorRecord> result = context.commitOffset(
             new OffsetCommitRequestData()
                 .setGroupId("foo")
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1212,10 +1213,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitResponseData.OffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1225,7 +1226,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1263,10 +1264,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitRequestData.OffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1278,10 +1279,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new OffsetCommitResponseData.OffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1291,7 +1292,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1331,7 +1332,7 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
                         .setPartitions(Arrays.asList(
@@ -1351,7 +1352,7 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new OffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitResponseData.OffsetCommitResponseTopic()
                         .setName("bar")
                         .setPartitions(Arrays.asList(
@@ -1367,7 +1368,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 1,
@@ -1405,10 +1406,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1420,10 +1421,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new TxnOffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1433,7 +1434,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1458,10 +1459,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1487,10 +1488,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1523,10 +1524,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(100)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1562,10 +1563,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(1)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1577,10 +1578,10 @@ public class OffsetMetadataManagerTest {
 
         assertEquals(
             new TxnOffsetCommitResponseData()
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitResponseData.TxnOffsetCommitResponseTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitResponseData.TxnOffsetCommitResponsePartition()
                                 .setPartitionIndex(0)
                                 .setErrorCode(Errors.NONE.code())
@@ -1590,7 +1591,7 @@ public class OffsetMetadataManagerTest {
         );
 
         assertEquals(
-            Collections.singletonList(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
+            List.of(GroupCoordinatorRecordHelpers.newOffsetCommitRecord(
                 "foo",
                 "bar",
                 0,
@@ -1615,10 +1616,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1644,10 +1645,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(10)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1683,10 +1684,10 @@ public class OffsetMetadataManagerTest {
                 .setGroupId("foo")
                 .setMemberId("member")
                 .setGenerationId(100)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new TxnOffsetCommitRequestData.TxnOffsetCommitRequestTopic()
                         .setName("bar")
-                        .setPartitions(Collections.singletonList(
+                        .setPartitions(List.of(
                             new TxnOffsetCommitRequestData.TxnOffsetCommitRequestPartition()
                                 .setPartitionIndex(0)
                                 .setCommittedOffset(100L)
@@ -1714,7 +1715,7 @@ public class OffsetMetadataManagerTest {
                 .setPartitionIndexes(Arrays.asList(0, 1)),
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("bar")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
         List<OffsetFetchResponseData.OffsetFetchResponseTopics> expectedResponse = Arrays.asList(
@@ -1726,7 +1727,7 @@ public class OffsetMetadataManagerTest {
                 )),
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("bar")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkInvalidOffsetPartitionResponse(0)
                 ))
         );
@@ -1744,7 +1745,7 @@ public class OffsetMetadataManagerTest {
                 .setPartitionIndexes(Arrays.asList(0, 1)),
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("bar")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
         List<OffsetFetchResponseData.OffsetFetchResponseTopics> expectedResponse = Arrays.asList(
@@ -1756,7 +1757,7 @@ public class OffsetMetadataManagerTest {
                 )),
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("bar")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkInvalidOffsetPartitionResponse(0)
                 ))
         );
@@ -2001,13 +2002,13 @@ public class OffsetMetadataManagerTest {
         );
         group.transitionTo(ClassicGroupState.DEAD);
 
-        assertEquals(Collections.emptyList(), context.fetchAllOffsets("group", Long.MAX_VALUE));
+        assertEquals(List.of(), context.fetchAllOffsets("group", Long.MAX_VALUE));
     }
 
     @Test
     public void testFetchAllOffsetsWithUnknownGroup() {
         OffsetMetadataManagerTestContext context = new OffsetMetadataManagerTestContext.Builder().build();
-        assertEquals(Collections.emptyList(), context.fetchAllOffsets("group", Long.MAX_VALUE));
+        assertEquals(List.of(), context.fetchAllOffsets("group", Long.MAX_VALUE));
     }
 
     @Test
@@ -2029,7 +2030,7 @@ public class OffsetMetadataManagerTest {
         assertEquals(5, context.lastWrittenOffset);
 
         // Fetching with 0 should no offsets.
-        assertEquals(Collections.emptyList(), context.fetchAllOffsets("group", 0L));
+        assertEquals(List.of(), context.fetchAllOffsets("group", 0L));
 
         // Fetching with 1 should return data up to offset 1.
         assertEquals(Arrays.asList(
@@ -2181,25 +2182,25 @@ public class OffsetMetadataManagerTest {
         context.commitOffset("group", "foo", 0, 100L, 1);
 
         // Fetch offsets case.
-        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = Collections.singletonList(
+        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = List.of(
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("foo")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
-        assertEquals(Collections.singletonList(
+        assertEquals(List.of(
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("foo")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkOffsetPartitionResponse(0, 100L, 1, "metadata")
                 ))
         ), context.fetchOffsets("group", "member", 0, topics, Long.MAX_VALUE));
 
         // Fetch all offsets case.
-        assertEquals(Collections.singletonList(
+        assertEquals(List.of(
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("foo")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkOffsetPartitionResponse(0, 100L, 1, "metadata")
                 ))
         ), context.fetchAllOffsets("group", "member", 0, Long.MAX_VALUE));
@@ -2216,25 +2217,25 @@ public class OffsetMetadataManagerTest {
         context.commitOffset("group", "foo", 0, 100L, 1);
 
         // Fetch offsets case.
-        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = Collections.singletonList(
+        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = List.of(
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("foo")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
-        assertEquals(Collections.singletonList(
+        assertEquals(List.of(
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("foo")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkOffsetPartitionResponse(0, 100L, 1, "metadata")
                 ))
         ), context.fetchOffsets("group", topics, Long.MAX_VALUE));
 
         // Fetch all offsets case.
-        assertEquals(Collections.singletonList(
+        assertEquals(List.of(
             new OffsetFetchResponseData.OffsetFetchResponseTopics()
                 .setName("foo")
-                .setPartitions(Collections.singletonList(
+                .setPartitions(List.of(
                     mkOffsetPartitionResponse(0, 100L, 1, "metadata")
                 ))
         ), context.fetchAllOffsets("group", Long.MAX_VALUE));
@@ -2246,10 +2247,10 @@ public class OffsetMetadataManagerTest {
         context.groupMetadataManager.getOrMaybeCreatePersistedConsumerGroup("group", true);
 
         // Fetch offsets case.
-        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = Collections.singletonList(
+        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = List.of(
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("foo")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
         // Fetch offsets cases.
@@ -2272,10 +2273,10 @@ public class OffsetMetadataManagerTest {
         group.updateMember(new ConsumerGroupMember.Builder("member").build());
 
         // Fetch offsets case.
-        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = Collections.singletonList(
+        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = List.of(
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("foo")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
         // Fetch offsets case.
@@ -2296,10 +2297,10 @@ public class OffsetMetadataManagerTest {
                 .build()
         );
 
-        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = Collections.singletonList(
+        List<OffsetFetchRequestData.OffsetFetchRequestTopics> topics = List.of(
             new OffsetFetchRequestData.OffsetFetchRequestTopics()
                 .setName("foo")
-                .setPartitionIndexes(Collections.singletonList(0))
+                .setPartitionIndexes(List.of(0))
         );
 
         // Fetch offsets case.
@@ -2319,7 +2320,7 @@ public class OffsetMetadataManagerTest {
             true
         );
         context.commitOffset("foo", "bar", 0, 100L, 0);
-        group.setSubscribedTopics(Optional.of(Collections.emptySet()));
+        group.setSubscribedTopics(Optional.of(Set.of()));
         context.testOffsetDeleteWith("foo", "bar", 0, Errors.NONE);
         assertFalse(context.hasOffset("foo", "bar", 0));
     }
@@ -2331,7 +2332,7 @@ public class OffsetMetadataManagerTest {
             "foo",
             true
         );
-        group.setSubscribedTopics(Optional.of(Collections.singleton("bar")));
+        group.setSubscribedTopics(Optional.of(Set.of("bar")));
         context.commitOffset("foo", "bar", 0, 100L, 0);
 
         // Delete the offset whose topic partition doesn't exist.
@@ -2348,7 +2349,7 @@ public class OffsetMetadataManagerTest {
             true
         );
         context.commitOffset(10L, "foo", "bar", 0, 100L, 0, context.time.milliseconds());
-        group.setSubscribedTopics(Optional.of(Collections.emptySet()));
+        group.setSubscribedTopics(Optional.of(Set.of()));
         context.testOffsetDeleteWith("foo", "bar", 0, Errors.NONE);
         assertFalse(context.hasOffset("foo", "bar", 0));
     }
@@ -2377,7 +2378,7 @@ public class OffsetMetadataManagerTest {
             .addRacks()
             .build();
         ConsumerGroupMember member1 = new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("bar"))
+            .setSubscribedTopicNames(List.of("bar"))
             .build();
         group.computeSubscriptionMetadata(
             group.computeSubscribedTopicNames(null, member1),
@@ -2469,7 +2470,7 @@ public class OffsetMetadataManagerTest {
 
         List<CoordinatorRecord> records = new ArrayList<>();
         assertTrue(context.cleanupExpiredOffsets("unknown-group-id", records));
-        assertEquals(Collections.emptyList(), records);
+        assertEquals(List.of(), records);
     }
 
     @Test
@@ -2500,7 +2501,7 @@ public class OffsetMetadataManagerTest {
 
         List<CoordinatorRecord> records = new ArrayList<>();
         assertFalse(context.cleanupExpiredOffsets("group-id", records));
-        assertEquals(Collections.emptyList(), records);
+        assertEquals(List.of(), records);
     }
 
     @Test
@@ -2524,7 +2525,7 @@ public class OffsetMetadataManagerTest {
         // firstTopic-0: group is still subscribed to firstTopic. Do not expire.
         // secondTopic-0: should expire as offset retention has passed.
         // secondTopic-1: has not passed offset retention. Do not expire.
-        List<CoordinatorRecord> expectedRecords = Collections.singletonList(
+        List<CoordinatorRecord> expectedRecords = List.of(
             GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord("group-id", "secondTopic", 0)
         );
 
@@ -2540,7 +2541,7 @@ public class OffsetMetadataManagerTest {
 
         // Expire secondTopic-1.
         context.time.sleep(500);
-        expectedRecords = Collections.singletonList(
+        expectedRecords = List.of(
             GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord("group-id", "secondTopic", 1)
         );
 
@@ -2589,7 +2590,7 @@ public class OffsetMetadataManagerTest {
         // foo-0 should not be expired because it has a pending transactional offset commit.
         List<CoordinatorRecord> records = new ArrayList<>();
         assertFalse(context.cleanupExpiredOffsets("group-id", records));
-        assertEquals(Collections.emptyList(), records);
+        assertEquals(List.of(), records);
     }
 
     private static OffsetFetchResponseData.OffsetFetchResponsePartitions mkOffsetPartitionResponse(
@@ -2972,7 +2973,7 @@ public class OffsetMetadataManagerTest {
                 .setMemberId("member")
                 .setGenerationIdOrMemberEpoch(1)
                 .setRetentionTimeMs(1234L)
-                .setTopics(Collections.singletonList(
+                .setTopics(List.of(
                     new OffsetCommitRequestData.OffsetCommitRequestTopic()
                         .setName("bar")
                         .setPartitions(Arrays.asList(
@@ -3010,7 +3011,7 @@ public class OffsetMetadataManagerTest {
         // firstTopic-0: group is still subscribed to firstTopic. Do not expire.
         // secondTopic-0: should expire as offset retention has passed.
         // secondTopic-1: has not passed offset retention. Do not expire.
-        List<CoordinatorRecord> expectedRecords = Collections.singletonList(
+        List<CoordinatorRecord> expectedRecords = List.of(
             GroupCoordinatorRecordHelpers.newOffsetCommitTombstoneRecord("group-id", "secondTopic", 0)
         );
 
@@ -3048,10 +3049,10 @@ public class OffsetMetadataManagerTest {
 
         context.commitOffset("foo", "bar", 0, 100L, 0);
         context.commitOffset("foo", "bar", 1, 150L, 0);
-        group.setSubscribedTopics(Optional.of(Collections.emptySet()));
+        group.setSubscribedTopics(Optional.of(Set.of()));
 
         OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection requestTopicCollection =
-            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(Collections.singletonList(
+            new OffsetDeleteRequestData.OffsetDeleteRequestTopicCollection(List.of(
                 new OffsetDeleteRequestData.OffsetDeleteRequestTopic()
                     .setName("bar")
                     .setPartitions(Arrays.asList(
@@ -3173,7 +3174,7 @@ public class OffsetMetadataManagerTest {
             5000,
             "consumer",
             new JoinGroupRequestData.JoinGroupRequestProtocolCollection(
-                Collections.singletonList(new JoinGroupRequestData.JoinGroupRequestProtocol()
+                List.of(new JoinGroupRequestData.JoinGroupRequestProtocol()
                     .setName("range")
                     .setMetadata(new byte[0])
                 ).iterator()

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/assignor/GroupSpecImplTest.java

@@ -25,7 +25,6 @@ import org.apache.kafka.coordinator.group.modern.MemberSubscriptionAndAssignment
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -108,6 +107,6 @@ public class GroupSpecImplTest {
         ));
 
         assertEquals(topicPartitions, groupSpec.memberAssignment(TEST_MEMBER).partitions());
-        assertEquals(Collections.emptyMap(), groupSpec.memberAssignment("unknown-member").partitions());
+        assertEquals(Map.of(), groupSpec.memberAssignment("unknown-member").partitions());
     }
 }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/assignor/OptimizedUniformAssignmentBuilderTest.java

@@ -29,7 +29,6 @@ import org.apache.kafka.coordinator.group.modern.TopicMetadata;
 import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -63,7 +62,7 @@ public class OptimizedUniformAssignmentBuilderTest {
     @Test
     public void testOneMemberNoTopicSubscription() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -73,12 +72,12 @@ public class OptimizedUniformAssignmentBuilderTest {
             )
         );
 
-        Map<String, MemberSubscriptionAndAssignmentImpl> members = Collections.singletonMap(
+        Map<String, MemberSubscriptionAndAssignmentImpl> members = Map.of(
             memberA,
             new MemberSubscriptionAndAssignmentImpl(
                 Optional.empty(),
                 Optional.empty(),
-                Collections.emptySet(),
+                Set.of(),
                 Assignment.EMPTY
             )
         );
@@ -86,7 +85,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         GroupAssignment groupAssignment = assignor.assign(
@@ -94,13 +93,13 @@ public class OptimizedUniformAssignmentBuilderTest {
             subscribedTopicMetadata
         );
 
-        assertEquals(Collections.emptyMap(), groupAssignment.members());
+        assertEquals(Map.of(), groupAssignment.members());
     }
 
     @Test
     public void testOneMemberSubscribedToNonexistentTopic() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -110,12 +109,12 @@ public class OptimizedUniformAssignmentBuilderTest {
             )
         );
 
-        Map<String, MemberSubscriptionAndAssignmentImpl> members = Collections.singletonMap(
+        Map<String, MemberSubscriptionAndAssignmentImpl> members = Map.of(
             memberA,
             new MemberSubscriptionAndAssignmentImpl(
                 Optional.empty(),
                 Optional.empty(),
-                Collections.singleton(topic2Uuid),
+                Set.of(topic2Uuid),
                 Assignment.EMPTY
             )
         );
@@ -123,7 +122,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         assertThrows(PartitionAssignorException.class,
@@ -172,7 +171,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -199,21 +198,21 @@ public class OptimizedUniformAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
         members.put(memberC, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
@@ -226,13 +225,13 @@ public class OptimizedUniformAssignmentBuilderTest {
             mkTopicAssignment(topic3Uuid, 1)
         ));
         expectedAssignment.put(memberC,
-            Collections.emptyMap()
+            Map.of()
         );
 
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -270,7 +269,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -563,7 +562,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic2Uuid),
+            Set.of(topic2Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic1Uuid, 0),
                 mkTopicAssignment(topic2Uuid, 0)
@@ -573,7 +572,7 @@ public class OptimizedUniformAssignmentBuilderTest {
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic2Uuid),
+            Set.of(topic2Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic1Uuid, 1),
                 mkTopicAssignment(topic2Uuid, 1)

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/assignor/RangeAssignorTest.java

@@ -32,7 +32,6 @@ import org.apache.kafka.coordinator.group.modern.TopicMetadata;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -62,7 +61,7 @@ public class RangeAssignorTest {
     @Test
     public void testOneMemberNoTopic() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -72,12 +71,12 @@ public class RangeAssignorTest {
             )
         );
 
-        Map<String, MemberSubscriptionAndAssignmentImpl> members = Collections.singletonMap(
+        Map<String, MemberSubscriptionAndAssignmentImpl> members = Map.of(
             memberA,
             new MemberSubscriptionAndAssignmentImpl(
                 Optional.empty(),
                 Optional.empty(),
-                Collections.emptySet(),
+                Set.of(),
                 Assignment.EMPTY
             )
         );
@@ -85,7 +84,7 @@ public class RangeAssignorTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         GroupAssignment groupAssignment = assignor.assign(
@@ -93,9 +92,9 @@ public class RangeAssignorTest {
             subscribedTopicMetadata
         );
 
-        Map<String, MemberAssignment> expectedAssignment = Collections.singletonMap(
+        Map<String, MemberAssignment> expectedAssignment = Map.of(
             memberA,
-            new MemberAssignmentImpl(Collections.emptyMap())
+            new MemberAssignmentImpl(Map.of())
         );
 
         assertEquals(expectedAssignment, groupAssignment.members());
@@ -104,7 +103,7 @@ public class RangeAssignorTest {
     @Test
     public void testOneMemberSubscribedToNonExistentTopic() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -114,7 +113,7 @@ public class RangeAssignorTest {
             )
         );
 
-        Map<String, MemberSubscriptionAndAssignmentImpl> members = Collections.singletonMap(
+        Map<String, MemberSubscriptionAndAssignmentImpl> members = Map.of(
             memberA,
             new MemberSubscriptionAndAssignmentImpl(
                 Optional.empty(),
@@ -127,7 +126,7 @@ public class RangeAssignorTest {
         GroupSpec groupSpec = new GroupSpecImpl(
             members,
             HOMOGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         assertThrows(PartitionAssignorException.class,
@@ -328,7 +327,7 @@ public class RangeAssignorTest {
     @Test
     public void testStaticMembership() throws PartitionAssignorException {
         SubscribedTopicDescriber subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -342,13 +341,13 @@ public class RangeAssignorTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceA"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceB"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
@@ -368,7 +367,7 @@ public class RangeAssignorTest {
         members.put("memberA1", new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceA"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
@@ -398,7 +397,7 @@ public class RangeAssignorTest {
     @Test
     public void testMixedStaticMembership() throws PartitionAssignorException {
         SubscribedTopicDescriber subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -413,13 +412,13 @@ public class RangeAssignorTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceA"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
         members.put(memberC, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceC"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
@@ -427,7 +426,7 @@ public class RangeAssignorTest {
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
@@ -447,7 +446,7 @@ public class RangeAssignorTest {
         members.put("memberA1", new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.of("instanceA"),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
@@ -545,7 +544,7 @@ public class RangeAssignorTest {
             mkTopicAssignment(topic2Uuid, 1)
         ));
         // Member C shouldn't get any assignment.
-        expectedAssignment.put(memberC, Collections.emptyMap());
+        expectedAssignment.put(memberC, Map.of());
 
         assertAssignment(expectedAssignment, computedAssignment);
     }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/assignor/UniformHeterogeneousAssignmentBuilderTest.java

@@ -31,7 +31,6 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -91,7 +90,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
     @Test
     public void testTwoMembersNoTopicSubscription() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -105,20 +104,20 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptySet(),
+            Set.of(),
             Assignment.EMPTY
         ));
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptySet(),
+            Set.of(),
             Assignment.EMPTY
         ));
 
         GroupSpec groupSpec = new TestGroupSpecImpl(
             members,
             HETEROGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         GroupAssignment groupAssignment = assignor.assign(
@@ -126,13 +125,13 @@ public class UniformHeterogeneousAssignmentBuilderTest {
             subscribedTopicMetadata
         );
 
-        assertEquals(Collections.emptyMap(), groupAssignment.members());
+        assertEquals(Map.of(), groupAssignment.members());
     }
 
     @Test
     public void testTwoMembersSubscribedToNonexistentTopics() {
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(
-            Collections.singletonMap(
+            Map.of(
                 topic1Uuid,
                 new TopicMetadata(
                     topic1Uuid,
@@ -146,20 +145,20 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic2Uuid),
+            Set.of(topic2Uuid),
             Assignment.EMPTY
         ));
 
         GroupSpec groupSpec = new TestGroupSpecImpl(
             members,
             HETEROGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
 
         assertThrows(
@@ -193,14 +192,14 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
         GroupSpec groupSpec = new TestGroupSpecImpl(
             members,
             HETEROGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -240,28 +239,28 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic3Uuid),
+            Set.of(topic3Uuid),
             Assignment.EMPTY
         ));
 
         members.put(memberC, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             Assignment.EMPTY
         ));
 
         GroupSpec groupSpec = new TestGroupSpecImpl(
             members,
             HETEROGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -276,7 +275,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
             mkTopicAssignment(topic3Uuid, 0)
         ));
         expectedAssignment.put(memberB,
-            Collections.emptyMap()
+            Map.of()
         );
         expectedAssignment.put(memberC, mkAssignment(
             mkTopicAssignment(topic1Uuid, 0, 1)
@@ -309,7 +308,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic1Uuid, 0, 1, 2)
             ))
@@ -456,7 +455,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic1Uuid, 0, 2),
                 mkTopicAssignment(topic2Uuid, 0)
@@ -542,7 +541,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic2Uuid),
+            Set.of(topic2Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic2Uuid, 3, 4, 5, 6)
             ))
@@ -594,7 +593,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberA, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.singleton(topic1Uuid),
+            Set.of(topic1Uuid),
             new Assignment(mkAssignment(
                 mkTopicAssignment(topic1Uuid, 0, 2),
                 mkTopicAssignment(topic2Uuid, 1, 3)
@@ -725,14 +724,14 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         members.put(memberB, new MemberSubscriptionAndAssignmentImpl(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptySet(),
+            Set.of(),
             Assignment.EMPTY
         ));
 
         GroupSpec groupSpec = new TestGroupSpecImpl(
             members,
             HETEROGENEOUS,
-            Collections.emptyMap()
+            Map.of()
         );
         SubscribedTopicDescriberImpl subscribedTopicMetadata = new SubscribedTopicDescriberImpl(topicMetadata);
 
@@ -745,7 +744,7 @@ public class UniformHeterogeneousAssignmentBuilderTest {
         expectedAssignment.put(memberA, mkAssignment(
             mkTopicAssignment(topic1Uuid, 0, 1, 2)
         ));
-        expectedAssignment.put(memberB, Collections.emptyMap());
+        expectedAssignment.put(memberB, Map.of());
 
         assertAssignment(expectedAssignment, computedAssignment);
     }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/classic/ClassicGroupTest.java

@@ -57,7 +57,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Optional;
@@ -429,7 +428,7 @@ public class ClassicGroupTest {
 
         group.initNextGeneration();
 
-        assertEquals(Optional.of(Collections.emptySet()), group.subscribedTopics());
+        assertEquals(Optional.of(Set.of()), group.subscribedTopics());
 
         protocols = new JoinGroupRequestProtocolCollection();
         protocols.add(new JoinGroupRequestProtocol()
@@ -852,7 +851,7 @@ public class ClassicGroupTest {
         assertTrue(group.addPendingSyncMember(memberId));
         assertEquals(Set.of(memberId), group.allPendingSyncMembers());
         group.removePendingSyncMember(memberId);
-        assertEquals(Collections.emptySet(), group.allPendingSyncMembers());
+        assertEquals(Set.of(), group.allPendingSyncMembers());
     }
 
     @Test
@@ -877,7 +876,7 @@ public class ClassicGroupTest {
         assertTrue(group.addPendingSyncMember(memberId));
         assertEquals(Set.of(memberId), group.allPendingSyncMembers());
         group.remove(memberId);
-        assertEquals(Collections.emptySet(), group.allPendingSyncMembers());
+        assertEquals(Set.of(), group.allPendingSyncMembers());
     }
 
     @Test
@@ -903,7 +902,7 @@ public class ClassicGroupTest {
         assertTrue(group.addPendingSyncMember(memberId));
         assertEquals(Set.of(memberId), group.allPendingSyncMembers());
         group.initNextGeneration();
-        assertEquals(Collections.emptySet(), group.allPendingSyncMembers());
+        assertEquals(Set.of(), group.allPendingSyncMembers());
     }
 
     @Test
@@ -1251,7 +1250,7 @@ public class ClassicGroupTest {
         group.transitionTo(PREPARING_REBALANCE);
         group.initNextGeneration();
         assertTrue(group.isInState(EMPTY));
-        assertEquals(Optional.of(Collections.emptySet()), group.computeSubscribedTopics());
+        assertEquals(Optional.of(Set.of()), group.computeSubscribedTopics());
         assertTrue(group.usesConsumerGroupProtocol());
         assertFalse(group.isSubscribedToTopic("topic"));
 
@@ -1458,7 +1457,7 @@ public class ClassicGroupTest {
 
         ClassicGroup classicGroup = ClassicGroup.fromConsumerGroup(
             consumerGroup,
-            Collections.emptySet(),
+            Set.of(),
             newMember2,
             logContext,
             time,

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/metrics/GroupCoordinatorMetricsTest.java

@@ -37,9 +37,9 @@ import com.yammer.metrics.core.MetricsRegistry;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.stream.IntStream;
 
 import static org.apache.kafka.coordinator.group.metrics.GroupCoordinatorMetrics.CLASSIC_GROUP_COMPLETED_REBALANCES_SENSOR_NAME;
@@ -77,43 +77,43 @@ public class GroupCoordinatorMetricsTest {
             metrics.metricName(
                 "group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", "classic")),
+                Map.of("protocol", "classic")),
             metrics.metricName(
                 "group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", "consumer")),
+                Map.of("protocol", "consumer")),
             metrics.metricName(
                 "consumer-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", ConsumerGroupState.EMPTY.toString())),
+                Map.of("state", ConsumerGroupState.EMPTY.toString())),
             metrics.metricName(
                 "consumer-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", ConsumerGroupState.ASSIGNING.toString())),
+                Map.of("state", ConsumerGroupState.ASSIGNING.toString())),
             metrics.metricName(
                 "consumer-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", ConsumerGroupState.RECONCILING.toString())),
+                Map.of("state", ConsumerGroupState.RECONCILING.toString())),
             metrics.metricName(
                 "consumer-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", ConsumerGroupState.STABLE.toString())),
+                Map.of("state", ConsumerGroupState.STABLE.toString())),
             metrics.metricName(
                 "consumer-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", ConsumerGroupState.DEAD.toString())),
+                Map.of("state", ConsumerGroupState.DEAD.toString())),
             metrics.metricName(
                 "group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", Group.GroupType.SHARE.toString())),
+                Map.of("protocol", Group.GroupType.SHARE.toString())),
             metrics.metricName(
                 "rebalance-rate",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", Group.GroupType.SHARE.toString())),
+                Map.of("protocol", Group.GroupType.SHARE.toString())),
             metrics.metricName(
                 "rebalance-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", Group.GroupType.SHARE.toString())),
+                Map.of("protocol", Group.GroupType.SHARE.toString())),
             metrics.metricName(
                 "share-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
@@ -132,33 +132,33 @@ public class GroupCoordinatorMetricsTest {
             metrics.metricName(
                 "group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("protocol", Group.GroupType.STREAMS.toString())),
+                Map.of("protocol", Group.GroupType.STREAMS.toString())),
             metrics.metricName("streams-group-rebalance-rate", GroupCoordinatorMetrics.METRICS_GROUP),
             metrics.metricName("streams-group-rebalance-count", GroupCoordinatorMetrics.METRICS_GROUP),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.EMPTY.toString())),
+                Map.of("state", StreamsGroupState.EMPTY.toString())),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.ASSIGNING.toString())),
+                Map.of("state", StreamsGroupState.ASSIGNING.toString())),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.RECONCILING.toString())),
+                Map.of("state", StreamsGroupState.RECONCILING.toString())),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.STABLE.toString())),
+                Map.of("state", StreamsGroupState.STABLE.toString())),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.DEAD.toString())),
+                Map.of("state", StreamsGroupState.DEAD.toString())),
             metrics.metricName(
                 "streams-group-count",
                 GroupCoordinatorMetrics.METRICS_GROUP,
-                Collections.singletonMap("state", StreamsGroupState.NOT_READY.toString()))
+                Map.of("state", StreamsGroupState.NOT_READY.toString()))
         ));
 
         try {
@@ -176,7 +176,7 @@ public class GroupCoordinatorMetricsTest {
                 assertMetricsForTypeEqual(registry, "kafka.coordinator.group", expectedRegistry);
                 expectedMetrics.forEach(metricName -> assertTrue(metrics.metrics().containsKey(metricName), metricName + " is missing"));
             }
-            assertMetricsForTypeEqual(registry, "kafka.coordinator.group", Collections.emptySet());
+            assertMetricsForTypeEqual(registry, "kafka.coordinator.group", Set.of());
             expectedMetrics.forEach(metricName -> assertFalse(metrics.metrics().containsKey(metricName)));
         } finally {
             registry.shutdown();
@@ -211,13 +211,13 @@ public class GroupCoordinatorMetricsTest {
             Utils.mkEntry(ClassicGroupState.DEAD, 1L)
         ));
 
-        shard0.setConsumerGroupGauges(Collections.singletonMap(ConsumerGroupState.ASSIGNING, 5L));
+        shard0.setConsumerGroupGauges(Map.of(ConsumerGroupState.ASSIGNING, 5L));
         shard1.setConsumerGroupGauges(Map.of(
             ConsumerGroupState.RECONCILING, 1L,
             ConsumerGroupState.DEAD, 1L
         ));
 
-        shard0.setStreamsGroupGauges(Collections.singletonMap(StreamsGroupState.ASSIGNING, 2L));
+        shard0.setStreamsGroupGauges(Map.of(StreamsGroupState.ASSIGNING, 2L));
         shard1.setStreamsGroupGauges(Map.of(
             StreamsGroupState.RECONCILING, 1L,
             StreamsGroupState.DEAD, 1L,
@@ -240,7 +240,7 @@ public class GroupCoordinatorMetricsTest {
         assertGaugeValue(registry, metricName("GroupMetadataManager", "NumGroups"), 9);
         assertGaugeValue(
             metrics,
-            metrics.metricName("group-count", METRICS_GROUP, Collections.singletonMap("protocol", "classic")),
+            metrics.metricName("group-count", METRICS_GROUP, Map.of("protocol", "classic")),
             9
         );
 
@@ -256,7 +256,7 @@ public class GroupCoordinatorMetricsTest {
         assertEquals(1, shard1.numOffsets());
         assertGaugeValue(
             metrics,
-            metrics.metricName("group-count", METRICS_GROUP, Collections.singletonMap("protocol", "consumer")),
+            metrics.metricName("group-count", METRICS_GROUP, Map.of("protocol", "consumer")),
             7
         );
         assertGaugeValue(registry, metricName("GroupMetadataManager", "NumOffsets"), 7);
@@ -265,7 +265,7 @@ public class GroupCoordinatorMetricsTest {
         assertEquals(6, shard1.numShareGroups());
         assertGaugeValue(
             metrics,
-            metrics.metricName("group-count", METRICS_GROUP, Collections.singletonMap("protocol", "share")),
+            metrics.metricName("group-count", METRICS_GROUP, Map.of("protocol", "share")),
             8
         );
         
@@ -273,7 +273,7 @@ public class GroupCoordinatorMetricsTest {
         assertEquals(3, shard1.numStreamsGroups());
         assertGaugeValue(
             metrics,
-            metrics.metricName("group-count", METRICS_GROUP, Collections.singletonMap("protocol", "streams")),
+            metrics.metricName("group-count", METRICS_GROUP, Map.of("protocol", "streams")),
             5
         );
     }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/TargetAssignmentBuilderTest.java

@@ -30,7 +30,6 @@ import org.apache.kafka.image.TopicsImage;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -323,11 +322,11 @@ public class TargetAssignmentBuilderTest {
         );
 
         TargetAssignmentBuilder.TargetAssignmentResult result = context.build();
-        assertEquals(Collections.singletonList(newConsumerGroupTargetAssignmentEpochRecord(
+        assertEquals(List.of(newConsumerGroupTargetAssignmentEpochRecord(
             "my-group",
             20
         )), result.records());
-        assertEquals(Collections.emptyMap(), result.targetAssignment());
+        assertEquals(Map.of(), result.targetAssignment());
     }
 
     @Test
@@ -362,7 +361,7 @@ public class TargetAssignmentBuilderTest {
 
         TargetAssignmentBuilder.TargetAssignmentResult result = context.build();
 
-        assertEquals(Collections.singletonList(newConsumerGroupTargetAssignmentEpochRecord(
+        assertEquals(List.of(newConsumerGroupTargetAssignmentEpochRecord(
             "my-group",
             20
         )), result.records());
@@ -870,10 +869,10 @@ public class TargetAssignmentBuilderTest {
 
         context.addGroupMember("member-2", Arrays.asList("foo", "bar", "zar"), mkAssignment());
 
-        context.addGroupMember("member-3", Collections.emptyList(), "foo*", mkAssignment());
+        context.addGroupMember("member-3", List.of(), "foo*", mkAssignment());
 
         context.addResolvedRegularExpression("foo*", new ResolvedRegularExpression(
-            Collections.singleton("foo"),
+            Set.of("foo"),
             10L,
             12345L
         ));

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/TopicIdsTest.java

@@ -22,7 +22,6 @@ import org.apache.kafka.image.TopicsImage;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -40,12 +39,12 @@ public class TopicIdsTest {
 
     @Test
     public void testTopicsImageCannotBeNull() {
-        assertThrows(NullPointerException.class, () -> new TopicIds(Collections.emptySet(), (TopicsImage) null));
+        assertThrows(NullPointerException.class, () -> new TopicIds(Set.of(), (TopicsImage) null));
     }
 
     @Test
     public void testTopicResolverCannotBeNull() {
-        assertThrows(NullPointerException.class, () -> new TopicIds(Collections.emptySet(), (TopicIds.TopicResolver) null));
+        assertThrows(NullPointerException.class, () -> new TopicIds(Set.of(), (TopicIds.TopicResolver) null));
     }
 
     @Test
@@ -57,7 +56,7 @@ public class TopicIdsTest {
 
     @Test
     public void testIsEmpty() {
-        Set<String> topicNames = Collections.emptySet();
+        Set<String> topicNames = Set.of();
         Set<Uuid> topicIds = new TopicIds(topicNames, TopicsImage.EMPTY);
         assertEquals(topicNames.size(), topicIds.size());
     }
@@ -176,14 +175,14 @@ public class TopicIdsTest {
     @Test
     public void testEquals() {
         Uuid topicId = Uuid.randomUuid();
-        TopicIds topicIds1 = new TopicIds(Collections.singleton("topic"),
+        TopicIds topicIds1 = new TopicIds(Set.of("topic"),
             new MetadataImageBuilder()
                 .addTopic(topicId, "topicId", 3)
                 .build()
                 .topics()
         );
 
-        TopicIds topicIds2 = new TopicIds(Collections.singleton("topic"),
+        TopicIds topicIds2 = new TopicIds(Set.of("topic"),
             new MetadataImageBuilder()
                 .addTopic(topicId, "topicId", 3)
                 .build()

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/UnionSetTest.java

@@ -20,7 +20,6 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.IntStream;
@@ -34,8 +33,8 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 public class UnionSetTest {
     @Test
     public void testSetsCannotBeNull() {
-        assertThrows(NullPointerException.class, () -> new UnionSet<String>(Collections.emptySet(), null));
+        assertThrows(NullPointerException.class, () -> new UnionSet<String>(Set.of(), null));
-        assertThrows(NullPointerException.class, () -> new UnionSet<String>(null, Collections.emptySet()));
+        assertThrows(NullPointerException.class, () -> new UnionSet<String>(null, Set.of()));
     }
 
     @Test
@@ -72,21 +71,21 @@ public class UnionSetTest {
 
         union = new UnionSet<>(
             Set.of(1, 2, 3),
-            Collections.emptySet()
+            Set.of()
         );
 
         assertFalse(union.isEmpty());
 
         union = new UnionSet<>(
-            Collections.emptySet(),
+            Set.of(),
             Set.of(2, 3, 4, 5)
         );
 
         assertFalse(union.isEmpty());
 
         union = new UnionSet<>(
-            Collections.emptySet(),
+            Set.of(),
-            Collections.emptySet()
+            Set.of()
         );
         assertTrue(union.isEmpty());
     }

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroupMemberTest.java

@@ -31,7 +31,6 @@ import org.junit.jupiter.params.provider.ValueSource;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -39,7 +38,6 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 import static org.apache.kafka.coordinator.group.AssignmentTestUtil.mkAssignment;
 import static org.apache.kafka.coordinator.group.AssignmentTestUtil.mkTopicAssignment;
@@ -178,7 +176,7 @@ public class ConsumerGroupMemberTest {
             .maybeUpdateRackId(Optional.of("new-rack-id"))
             .maybeUpdateInstanceId(Optional.of("new-instance-id"))
             .maybeUpdateServerAssignorName(Optional.of("new-assignor"))
-            .maybeUpdateSubscribedTopicNames(Optional.of(Collections.singletonList("zar")))
+            .maybeUpdateSubscribedTopicNames(Optional.of(List.of("zar")))
             .maybeUpdateSubscribedTopicRegex(Optional.of("new-regex"))
             .maybeUpdateRebalanceTimeoutMs(OptionalInt.of(6000))
             .build();
@@ -231,10 +229,10 @@ public class ConsumerGroupMemberTest {
         ConsumerGroupCurrentMemberAssignmentValue record = new ConsumerGroupCurrentMemberAssignmentValue()
             .setMemberEpoch(10)
             .setPreviousMemberEpoch(9)
-            .setAssignedPartitions(Collections.singletonList(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
+            .setAssignedPartitions(List.of(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
                 .setTopicId(topicId1)
                 .setPartitions(Arrays.asList(0, 1, 2))))
-            .setPartitionsPendingRevocation(Collections.singletonList(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
+            .setPartitionsPendingRevocation(List.of(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
                 .setTopicId(topicId2)
                 .setPartitions(Arrays.asList(3, 4, 5))));
 
@@ -266,10 +264,10 @@ public class ConsumerGroupMemberTest {
         ConsumerGroupCurrentMemberAssignmentValue record = new ConsumerGroupCurrentMemberAssignmentValue()
             .setMemberEpoch(epoch)
             .setPreviousMemberEpoch(epoch - 1)
-            .setAssignedPartitions(Collections.singletonList(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
+            .setAssignedPartitions(List.of(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
                 .setTopicId(topicId1)
                 .setPartitions(assignedPartitions)))
-            .setPartitionsPendingRevocation(Collections.singletonList(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
+            .setPartitionsPendingRevocation(List.of(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
                 .setTopicId(topicId2)
                 .setPartitions(Arrays.asList(3, 4, 5))));
         String memberId = Uuid.randomUuid().toString();
@@ -306,7 +304,7 @@ public class ConsumerGroupMemberTest {
             .setSubscribedTopicRegex(subscribedTopicRegex)
             .setAssignment(
                 new ConsumerGroupDescribeResponseData.Assignment()
-                    .setTopicPartitions(Collections.singletonList(new ConsumerGroupDescribeResponseData.TopicPartitions()
+                    .setTopicPartitions(List.of(new ConsumerGroupDescribeResponseData.TopicPartitions()
                         .setTopicId(topicId1)
                         .setTopicName("topic1")
                         .setPartitions(assignedPartitions)
@@ -319,7 +317,7 @@ public class ConsumerGroupMemberTest {
                             .setTopicId(item.getKey())
                             .setTopicName("topic4")
                             .setPartitions(new ArrayList<>(item.getValue()))
-                    ).collect(Collectors.toList()))
+                    ).toList())
             )
             .setMemberType(withClassicMemberMetadata ? (byte) 0 : (byte) 1);
 
@@ -341,7 +339,7 @@ public class ConsumerGroupMemberTest {
     public void testAsConsumerGroupDescribeWithTopicNameNotFound() {
         Uuid memberId = Uuid.randomUuid();
         ConsumerGroupCurrentMemberAssignmentValue record = new ConsumerGroupCurrentMemberAssignmentValue()
-            .setAssignedPartitions(Collections.singletonList(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
+            .setAssignedPartitions(List.of(new ConsumerGroupCurrentMemberAssignmentValue.TopicPartitions()
                 .setTopicId(Uuid.randomUuid())
                 .setPartitions(Arrays.asList(0, 1, 2))));
         ConsumerGroupMember member = new ConsumerGroupMember.Builder(memberId.toString())

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroupTest.java

@@ -57,7 +57,6 @@ import org.junit.jupiter.params.provider.CsvSource;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -247,7 +246,7 @@ public class ConsumerGroupTest {
 
         member = new ConsumerGroupMember.Builder("member")
             .setMemberEpoch(10)
-            .setAssignedPartitions(Collections.emptyMap())
+            .setAssignedPartitions(Map.of())
             .setPartitionsPendingRevocation(mkAssignment(
                 mkTopicAssignment(fooTopicId, 1)))
             .build();
@@ -260,7 +259,7 @@ public class ConsumerGroupTest {
             .setMemberEpoch(11)
             .setAssignedPartitions(mkAssignment(
                 mkTopicAssignment(fooTopicId, 1)))
-            .setPartitionsPendingRevocation(Collections.emptyMap())
+            .setPartitionsPendingRevocation(Map.of())
             .build();
 
         consumerGroup.updateMember(member);
@@ -641,20 +640,20 @@ public class ConsumerGroupTest {
             .build();
 
         ConsumerGroupMember member1 = new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ConsumerGroupMember member2 = new ConsumerGroupMember.Builder("member2")
-            .setSubscribedTopicNames(Collections.singletonList("bar"))
+            .setSubscribedTopicNames(List.of("bar"))
             .build();
         ConsumerGroupMember member3 = new ConsumerGroupMember.Builder("member3")
-            .setSubscribedTopicNames(Collections.singletonList("zar"))
+            .setSubscribedTopicNames(List.of("zar"))
             .build();
 
         ConsumerGroup consumerGroup = createConsumerGroup("group-foo");
 
         // It should be empty by default.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             consumerGroup.computeSubscriptionMetadata(
                 consumerGroup.computeSubscribedTopicNames(null, null),
                 image.topics(),
@@ -691,7 +690,7 @@ public class ConsumerGroupTest {
 
         // Compute while taking into account removal of member 1.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             consumerGroup.computeSubscriptionMetadata(
                 consumerGroup.computeSubscribedTopicNames(member1, null),
                 image.topics(),
@@ -785,7 +784,7 @@ public class ConsumerGroupTest {
 
         // Compute while taking into account removal of member 1, member 2 and member 3
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             consumerGroup.computeSubscriptionMetadata(
                 consumerGroup.computeSubscribedTopicNames(new HashSet<>(Arrays.asList(member1, member2, member3))),
                 image.topics(),
@@ -812,7 +811,7 @@ public class ConsumerGroupTest {
                 mkEntry("zar", new TopicMetadata(zarTopicId, "zar", 3))
             ),
             consumerGroup.computeSubscriptionMetadata(
-                consumerGroup.computeSubscribedTopicNames(Collections.singleton(member1)),
+                consumerGroup.computeSubscribedTopicNames(Set.of(member1)),
                 image.topics(),
                 image.cluster()
             )
@@ -826,7 +825,7 @@ public class ConsumerGroupTest {
                 mkEntry("zar", new TopicMetadata(zarTopicId, "zar", 3))
             ),
             consumerGroup.computeSubscriptionMetadata(
-                consumerGroup.computeSubscribedTopicNames(Collections.emptySet()),
+                consumerGroup.computeSubscribedTopicNames(Set.of()),
                 image.topics(),
                 image.cluster()
             )
@@ -836,7 +835,7 @@ public class ConsumerGroupTest {
     @Test
     public void testUpdateSubscribedTopicNamesAndSubscriptionType() {
         ConsumerGroupMember member1 = new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ConsumerGroupMember member2 = new ConsumerGroupMember.Builder("member2")
             .setSubscribedTopicNames(Arrays.asList("bar", "foo"))
@@ -849,7 +848,7 @@ public class ConsumerGroupTest {
 
         // It should be empty by default.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             consumerGroup.subscribedTopicNames()
         );
 
@@ -910,9 +909,9 @@ public class ConsumerGroupTest {
         String memberId2 = "member2";
 
         // Initial assignment for member1
-        Assignment initialAssignment = new Assignment(Collections.singletonMap(
+        Assignment initialAssignment = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(0))
+            new HashSet<>(List.of(0))
         ));
         consumerGroup.updateTargetAssignment(memberId1, initialAssignment);
 
@@ -925,9 +924,9 @@ public class ConsumerGroupTest {
         );
 
         // New assignment for member1
-        Assignment newAssignment = new Assignment(Collections.singletonMap(
+        Assignment newAssignment = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(1))
+            new HashSet<>(List.of(1))
         ));
         consumerGroup.updateTargetAssignment(memberId1, newAssignment);
 
@@ -940,9 +939,9 @@ public class ConsumerGroupTest {
         );
 
         // New assignment for member2 to add partition 1
-        Assignment newAssignment2 = new Assignment(Collections.singletonMap(
+        Assignment newAssignment2 = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(1))
+            new HashSet<>(List.of(1))
         ));
         consumerGroup.updateTargetAssignment(memberId2, newAssignment2);
 
@@ -955,9 +954,9 @@ public class ConsumerGroupTest {
         );
 
         // New assignment for member1 to revoke partition 1 and assign partition 0
-        Assignment newAssignment1 = new Assignment(Collections.singletonMap(
+        Assignment newAssignment1 = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(0))
+            new HashSet<>(List.of(0))
         ));
         consumerGroup.updateTargetAssignment(memberId1, newAssignment1);
 
@@ -1121,14 +1120,14 @@ public class ConsumerGroupTest {
         SnapshotRegistry snapshotRegistry = new SnapshotRegistry(new LogContext());
         GroupCoordinatorMetricsShard metricsShard = new GroupCoordinatorMetricsShard(
             snapshotRegistry,
-            Collections.emptyMap(),
+            Map.of(),
             new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)
         );
         ConsumerGroup group = new ConsumerGroup(snapshotRegistry, "group-foo", metricsShard);
         snapshotRegistry.idempotentCreateSnapshot(0);
         assertEquals(ConsumerGroup.ConsumerGroupState.EMPTY.toString(), group.stateAsString(0));
         group.updateMember(new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
         assertEquals(ConsumerGroup.ConsumerGroupState.EMPTY.toString(), group.stateAsString(0));
@@ -1222,10 +1221,10 @@ public class ConsumerGroupTest {
             .build();
 
         ConsumerGroupMember member1 = new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ConsumerGroupMember member2 = new ConsumerGroupMember.Builder("member2")
-            .setSubscribedTopicNames(Collections.singletonList("bar"))
+            .setSubscribedTopicNames(List.of("bar"))
             .build();
 
         ConsumerGroup consumerGroup = createConsumerGroup("group-foo");
@@ -1263,7 +1262,7 @@ public class ConsumerGroupTest {
         assertEquals(ConsumerGroup.ConsumerGroupState.EMPTY.toString(), group.stateAsString(0));
 
         group.updateMember(new ConsumerGroupMember.Builder("member1")
-                .setSubscribedTopicNames(Collections.singletonList("foo"))
+                .setSubscribedTopicNames(List.of("foo"))
                 .setServerAssignorName("assignorName")
                 .build());
         group.updateMember(new ConsumerGroupMember.Builder("member2")
@@ -1279,7 +1278,7 @@ public class ConsumerGroupTest {
             .setMembers(Arrays.asList(
                 new ConsumerGroupDescribeResponseData.Member()
                     .setMemberId("member1")
-                    .setSubscribedTopicNames(Collections.singletonList("foo"))
+                    .setSubscribedTopicNames(List.of("foo"))
                     .setSubscribedTopicRegex("")
                     .setMemberType((byte) 1),
                 new ConsumerGroupDescribeResponseData.Member().setMemberId("member2")
@@ -1297,21 +1296,21 @@ public class ConsumerGroupTest {
         SnapshotRegistry snapshotRegistry = new SnapshotRegistry(new LogContext());
         GroupCoordinatorMetricsShard metricsShard = new GroupCoordinatorMetricsShard(
             snapshotRegistry,
-            Collections.emptyMap(),
+            Map.of(),
             new TopicPartition(Topic.GROUP_METADATA_TOPIC_NAME, 0)
         );
         ConsumerGroup group = new ConsumerGroup(snapshotRegistry, "group-foo", metricsShard);
         snapshotRegistry.idempotentCreateSnapshot(0);
-        assertTrue(group.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(group.isInStates(Set.of("empty"), 0));
-        assertFalse(group.isInStates(Collections.singleton("Empty"), 0));
+        assertFalse(group.isInStates(Set.of("Empty"), 0));
 
         group.updateMember(new ConsumerGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
-        assertTrue(group.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(group.isInStates(Set.of("empty"), 0));
-        assertTrue(group.isInStates(Collections.singleton("stable"), 1));
+        assertTrue(group.isInStates(Set.of("stable"), 1));
-        assertFalse(group.isInStates(Collections.singleton("empty"), 1));
+        assertFalse(group.isInStates(Set.of("empty"), 1));
     }
 
     @Test
@@ -1512,7 +1511,7 @@ public class ConsumerGroupTest {
             5000,
             500,
             ConsumerProtocol.PROTOCOL_TYPE,
-            new JoinGroupRequestData.JoinGroupRequestProtocolCollection(Collections.singletonList(
+            new JoinGroupRequestData.JoinGroupRequestProtocolCollection(List.of(
                 new JoinGroupRequestData.JoinGroupRequestProtocol()
                     .setName("range")
                     .setMetadata(Utils.toArray(ConsumerProtocol.serializeSubscription(new ConsumerPartitionAssignor.Subscription(
@@ -1562,7 +1561,7 @@ public class ConsumerGroupTest {
             .setClassicMemberMetadata(
                 new ConsumerGroupMemberMetadataValue.ClassicMemberMetadata()
                     .setSessionTimeoutMs(member.sessionTimeoutMs())
-                    .setSupportedProtocols(Collections.singletonList(
+                    .setSupportedProtocols(List.of(
                         new ConsumerGroupMemberMetadataValue.ClassicProtocol()
                             .setName("range")
                             .setMetadata(Utils.toArray(ConsumerProtocol.serializeSubscription(new ConsumerPartitionAssignor.Subscription(
@@ -1927,7 +1926,7 @@ public class ConsumerGroupTest {
             consumerGroup.computeSubscribedTopicNames(
                 member3,
                 new ConsumerGroupMember.Builder(member3)
-                    .setSubscribedTopicNames(Collections.emptyList())
+                    .setSubscribedTopicNames(List.of())
                     .build()
             )
         );
@@ -1942,7 +1941,7 @@ public class ConsumerGroupTest {
             consumerGroup.computeSubscribedTopicNames(
                 member3,
                 new ConsumerGroupMember.Builder(member3)
-                    .setSubscribedTopicNames(Collections.emptyList())
+                    .setSubscribedTopicNames(List.of())
                     .setSubscribedTopicRegex("")
                     .build()
             )
@@ -2122,8 +2121,8 @@ public class ConsumerGroupTest {
         assertEquals(
             HOMOGENEOUS,
             ConsumerGroup.subscriptionType(
-                Collections.emptyMap(),
+                Map.of(),
-                Collections.emptyMap(),
+                Map.of(),
                 0
             )
         );
@@ -2131,7 +2130,7 @@ public class ConsumerGroupTest {
         assertEquals(
             HOMOGENEOUS,
             ConsumerGroup.subscriptionType(
-                Collections.emptyMap(),
+                Map.of(),
                 Map.of("foo", new SubscriptionCount(5, 0)),
                 5
             )
@@ -2140,7 +2139,7 @@ public class ConsumerGroupTest {
         assertEquals(
             HETEROGENEOUS,
             ConsumerGroup.subscriptionType(
-                Collections.emptyMap(),
+                Map.of(),
                 Map.of(
                     "foo", new SubscriptionCount(4, 0),
                     "bar", new SubscriptionCount(1, 0)

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/consumer/CurrentAssignmentBuilderTest.java

@@ -25,7 +25,7 @@ import org.apache.kafka.coordinator.group.modern.MemberState;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
+import java.util.List;
 
 import static org.apache.kafka.coordinator.group.AssignmentTestUtil.mkAssignment;
 import static org.apache.kafka.coordinator.group.AssignmentTestUtil.mkTopicAssignment;
@@ -194,7 +194,7 @@ public class CurrentAssignmentBuilderTest {
             .withCurrentPartitionEpoch((topicId, __) ->
                 topicId2.equals(topicId) ? 10 : -1
             )
-            .withOwnedTopicPartitions(Collections.emptyList())
+            .withOwnedTopicPartitions(List.of())
             .build();
 
         assertEquals(
@@ -560,7 +560,7 @@ public class CurrentAssignmentBuilderTest {
                 mkTopicAssignment(topicId1, 3),
                 mkTopicAssignment(topicId2, 6))))
             .withCurrentPartitionEpoch((topicId, partitionId) -> 11)
-            .withOwnedTopicPartitions(Collections.emptyList())
+            .withOwnedTopicPartitions(List.of())
             .build();
 
         assertEquals(

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/share/ShareGroupMemberTest.java

@@ -25,7 +25,6 @@ import org.apache.kafka.image.MetadataImage;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
@@ -117,7 +116,7 @@ public class ShareGroupMemberTest {
 
         updatedMember = new ShareGroupMember.Builder(member)
             .maybeUpdateRackId(Optional.of("new-rack-id"))
-            .maybeUpdateSubscribedTopicNames(Optional.of(Collections.singletonList("zar")))
+            .maybeUpdateSubscribedTopicNames(Optional.of(List.of("zar")))
             .build();
 
         assertNull(member.instanceId());
@@ -180,7 +179,7 @@ public class ShareGroupMemberTest {
             .setSubscribedTopicNames(subscribedTopicNames)
             .setAssignment(
                 new ShareGroupDescribeResponseData.Assignment()
-                    .setTopicPartitions(Collections.singletonList(new ShareGroupDescribeResponseData.TopicPartitions()
+                    .setTopicPartitions(List.of(new ShareGroupDescribeResponseData.TopicPartitions()
                         .setTopicId(topicId1)
                         .setTopicName("topic1")
                         .setPartitions(assignedPartitions)

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/modern/share/ShareGroupTest.java

@@ -38,8 +38,10 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
 
 import static org.apache.kafka.common.utils.Utils.mkEntry;
 import static org.apache.kafka.common.utils.Utils.mkMap;
@@ -156,20 +158,20 @@ public class ShareGroupTest {
             .build();
 
         ShareGroupMember member1 = new ShareGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ShareGroupMember member2 = new ShareGroupMember.Builder("member2")
-            .setSubscribedTopicNames(Collections.singletonList("bar"))
+            .setSubscribedTopicNames(List.of("bar"))
             .build();
         ShareGroupMember member3 = new ShareGroupMember.Builder("member3")
-            .setSubscribedTopicNames(Collections.singletonList("zar"))
+            .setSubscribedTopicNames(List.of("zar"))
             .build();
 
         ShareGroup shareGroup = createShareGroup("group-foo");
 
         // It should be empty by default.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             shareGroup.computeSubscriptionMetadata(
                 shareGroup.computeSubscribedTopicNames(null, null),
                 image.topics(),
@@ -206,7 +208,7 @@ public class ShareGroupTest {
 
         // Compute while taking into account removal of member 1.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             shareGroup.computeSubscriptionMetadata(
                 shareGroup.computeSubscribedTopicNames(member1, null),
                 image.topics(),
@@ -300,7 +302,7 @@ public class ShareGroupTest {
 
         // Compute while taking into account removal of member 1, member 2 and member 3
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             shareGroup.computeSubscriptionMetadata(
                 shareGroup.computeSubscribedTopicNames(new HashSet<>(Arrays.asList(member1, member2, member3))),
                 image.topics(),
@@ -327,7 +329,7 @@ public class ShareGroupTest {
                 mkEntry("zar", new TopicMetadata(zarTopicId, "zar", 3))
             ),
             shareGroup.computeSubscriptionMetadata(
-                shareGroup.computeSubscribedTopicNames(Collections.singleton(member1)),
+                shareGroup.computeSubscribedTopicNames(Set.of(member1)),
                 image.topics(),
                 image.cluster()
             )
@@ -341,7 +343,7 @@ public class ShareGroupTest {
                 mkEntry("zar", new TopicMetadata(zarTopicId, "zar", 3))
             ),
             shareGroup.computeSubscriptionMetadata(
-                shareGroup.computeSubscribedTopicNames(Collections.emptySet()),
+                shareGroup.computeSubscribedTopicNames(Set.of()),
                 image.topics(),
                 image.cluster()
             )
@@ -351,7 +353,7 @@ public class ShareGroupTest {
     @Test
     public void testUpdateSubscribedTopicNamesAndSubscriptionType() {
         ShareGroupMember member1 = new ShareGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ShareGroupMember member2 = new ShareGroupMember.Builder("member2")
             .setSubscribedTopicNames(Arrays.asList("bar", "foo"))
@@ -364,7 +366,7 @@ public class ShareGroupTest {
 
         // It should be empty by default.
         assertEquals(
-            Collections.emptyMap(),
+            Map.of(),
             shareGroup.subscribedTopicNames()
         );
 
@@ -424,9 +426,9 @@ public class ShareGroupTest {
         String memberId2 = "member2";
 
         // Initial assignment for member1
-        Assignment initialAssignment = new Assignment(Collections.singletonMap(
+        Assignment initialAssignment = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(0))
+            new HashSet<>(List.of(0))
         ));
         shareGroup.updateTargetAssignment(memberId1, initialAssignment);
 
@@ -439,9 +441,9 @@ public class ShareGroupTest {
         );
 
         // New assignment for member1
-        Assignment newAssignment = new Assignment(Collections.singletonMap(
+        Assignment newAssignment = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(1))
+            new HashSet<>(List.of(1))
         ));
         shareGroup.updateTargetAssignment(memberId1, newAssignment);
 
@@ -454,9 +456,9 @@ public class ShareGroupTest {
         );
 
         // New assignment for member2 to add partition 1
-        Assignment newAssignment2 = new Assignment(Collections.singletonMap(
+        Assignment newAssignment2 = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(1))
+            new HashSet<>(List.of(1))
         ));
         shareGroup.updateTargetAssignment(memberId2, newAssignment2);
 
@@ -469,9 +471,9 @@ public class ShareGroupTest {
         );
 
         // New assignment for member1 to revoke partition 1 and assign partition 0
-        Assignment newAssignment1 = new Assignment(Collections.singletonMap(
+        Assignment newAssignment1 = new Assignment(Map.of(
             topicId,
-            new HashSet<>(Collections.singletonList(0))
+            new HashSet<>(List.of(0))
         ));
         shareGroup.updateTargetAssignment(memberId1, newAssignment1);
 
@@ -563,7 +565,7 @@ public class ShareGroupTest {
         assertEquals(ShareGroupState.EMPTY, shareGroup.state(0));
         assertEquals("Empty", shareGroup.stateAsString(0));
         shareGroup.updateMember(new ShareGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
         assertEquals(ShareGroupState.EMPTY, shareGroup.state(0));
@@ -630,10 +632,10 @@ public class ShareGroupTest {
             .build();
 
         ShareGroupMember member1 = new ShareGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build();
         ShareGroupMember member2 = new ShareGroupMember.Builder("member2")
-            .setSubscribedTopicNames(Collections.singletonList("bar"))
+            .setSubscribedTopicNames(List.of("bar"))
             .build();
 
         ShareGroup shareGroup = createShareGroup("group-foo");
@@ -671,7 +673,7 @@ public class ShareGroupTest {
         assertEquals(ShareGroupState.EMPTY.toString(), shareGroup.stateAsString(0));
 
         shareGroup.updateMember(new ShareGroupMember.Builder("member1")
-                .setSubscribedTopicNames(Collections.singletonList("foo"))
+                .setSubscribedTopicNames(List.of("foo"))
                 .build());
         shareGroup.updateMember(new ShareGroupMember.Builder("member2")
                 .build());
@@ -686,7 +688,7 @@ public class ShareGroupTest {
             .setMembers(Arrays.asList(
                 new ShareGroupDescribeResponseData.Member()
                     .setMemberId("member1")
-                    .setSubscribedTopicNames(Collections.singletonList("foo")),
+                    .setSubscribedTopicNames(List.of("foo")),
                 new ShareGroupDescribeResponseData.Member().setMemberId("member2")
             ));
         ShareGroupDescribeResponseData.DescribedGroup actual = shareGroup.asDescribedGroup(1, "assignorName",
@@ -700,16 +702,16 @@ public class ShareGroupTest {
         SnapshotRegistry snapshotRegistry = new SnapshotRegistry(new LogContext());
         ShareGroup shareGroup = new ShareGroup(snapshotRegistry, "group-foo");
         snapshotRegistry.idempotentCreateSnapshot(0);
-        assertTrue(shareGroup.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(shareGroup.isInStates(Set.of("empty"), 0));
-        assertFalse(shareGroup.isInStates(Collections.singleton("Empty"), 0));
+        assertFalse(shareGroup.isInStates(Set.of("Empty"), 0));
 
         shareGroup.updateMember(new ShareGroupMember.Builder("member1")
-            .setSubscribedTopicNames(Collections.singletonList("foo"))
+            .setSubscribedTopicNames(List.of("foo"))
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
-        assertTrue(shareGroup.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(shareGroup.isInStates(Set.of("empty"), 0));
-        assertTrue(shareGroup.isInStates(Collections.singleton("stable"), 1));
+        assertTrue(shareGroup.isInStates(Set.of("stable"), 1));
-        assertFalse(shareGroup.isInStates(Collections.singleton("empty"), 1));
+        assertFalse(shareGroup.isInStates(Set.of("empty"), 1));
     }
 
     private ShareGroup createShareGroup(String groupId) {

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/CurrentAssignmentBuilderTest.java

@@ -24,7 +24,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.EnumSource;
 
-import java.util.Collections;
+import java.util.Set;
 
 import static org.apache.kafka.coordinator.group.streams.TaskAssignmentTestUtil.mkTasks;
 import static org.apache.kafka.coordinator.group.streams.TaskAssignmentTestUtil.mkTasksTuple;
@@ -63,8 +63,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 3, 4)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -108,8 +108,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 3, 4)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -150,8 +150,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 3, 4, 7)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -191,8 +191,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 4, 5)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -235,8 +235,8 @@ public class CurrentAssignmentBuilderTest {
             .withTargetAssignment(memberEpoch + 1, TasksTuple.EMPTY)
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -278,8 +278,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 3, 4, 7)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -321,8 +321,8 @@ public class CurrentAssignmentBuilderTest {
                 SUBTOPOLOGY_ID2.equals(subtopologyId) ? PROCESS_ID : null
             )
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .withOwnedAssignment(mkTasksTuple(taskRole))
             .build();
 
@@ -365,8 +365,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .withOwnedAssignment(mkTasksTuple(taskRole,
                 mkTasks(SUBTOPOLOGY_ID1, 2, 3),
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6)))
@@ -412,9 +412,9 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 6)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
             .withCurrentWarmupTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet());
+                (subtopologyId, partitionId) -> Set.of());
 
         assertEquals(
             member,
@@ -511,8 +511,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6, 7)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .withOwnedAssignment(mkTasksTuple(taskRole,
                 mkTasks(SUBTOPOLOGY_ID1, 2, 3),
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6))
@@ -556,9 +556,9 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.singleton(PROCESS_ID))
+                (subtopologyId, partitionId) -> Set.of(PROCESS_ID))
             .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) ->
-                Collections.singleton(PROCESS_ID))
+                Set.of(PROCESS_ID))
             .build();
 
         assertEquals(
@@ -598,8 +598,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6, 7)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -639,9 +639,9 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 5, 6, 7)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.singleton(PROCESS_ID))
+                (subtopologyId, partitionId) -> Set.of(PROCESS_ID))
             .withCurrentWarmupTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.singleton(PROCESS_ID))
+                (subtopologyId, partitionId) -> Set.of(PROCESS_ID))
             .build();
 
         assertEquals(member, updatedMember);
@@ -671,10 +671,10 @@ public class CurrentAssignmentBuilderTest {
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> null)
             .withCurrentStandbyTaskProcessIds(
                 (subtopologyId, partitionId) -> (taskRole == TaskRole.STANDBY)
-                    ? Collections.emptySet() : Collections.singleton(PROCESS_ID))
+                    ? Set.of() : Set.of(PROCESS_ID))
             .withCurrentWarmupTaskProcessIds(
                 (subtopologyId, partitionId) -> (taskRole == TaskRole.STANDBY)
-                    ? Collections.singleton(PROCESS_ID) : Collections.emptySet())
+                    ? Set.of(PROCESS_ID) : Set.of())
             .build();
 
         assertEquals(member, updatedMember);
@@ -716,9 +716,9 @@ public class CurrentAssignmentBuilderTest {
                 (subtopologyId.equals(SUBTOPOLOGY_ID1) && partitionId == 4) ? "anyOtherProcess"
                     : null)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
             .withCurrentWarmupTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(expectedMember, updatedMember);
@@ -748,8 +748,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 6)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .build();
 
         assertEquals(
@@ -803,8 +803,8 @@ public class CurrentAssignmentBuilderTest {
                 mkTasks(SUBTOPOLOGY_ID2, 6)))
             .withCurrentActiveTaskProcessId((subtopologyId, partitionId) -> PROCESS_ID)
             .withCurrentStandbyTaskProcessIds(
-                (subtopologyId, partitionId) -> Collections.emptySet())
+                (subtopologyId, partitionId) -> Set.of())
-            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Collections.emptySet())
+            .withCurrentWarmupTaskProcessIds((subtopologyId, partitionId) -> Set.of())
             .withOwnedAssignment(mkTasksTuple(taskRole))
             .build();
 

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/StreamsGroupMemberTest.java

@@ -155,7 +155,7 @@ public class StreamsGroupMemberTest {
             .setUserEndpoint(USER_ENDPOINT)
             .setClientTags(CLIENT_TAGS.entrySet().stream()
                 .map(e -> new KeyValue().setKey(e.getKey()).setValue(e.getValue()))
-                .collect(Collectors.toList()));
+                .toList());
 
         StreamsGroupMember member = new StreamsGroupMember.Builder("member-id")
             .updateWith(record)

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/StreamsGroupTest.java

@@ -68,7 +68,6 @@ import java.util.OptionalLong;
 import java.util.Set;
 import java.util.stream.Collectors;
 
-import static java.util.Collections.emptyMap;
 import static org.apache.kafka.coordinator.group.streams.TaskAssignmentTestUtil.mkTasks;
 import static org.apache.kafka.coordinator.group.streams.TaskAssignmentTestUtil.mkTasksPerSubtopology;
 import static org.apache.kafka.coordinator.group.streams.TaskAssignmentTestUtil.mkTasksTuple;
@@ -221,19 +220,19 @@ public class StreamsGroupTest {
         streamsGroup.updateMember(member);
 
         assertEquals("process", streamsGroup.currentActiveTaskProcessId(fooSubtopology, 1));
-        assertEquals(Collections.singleton("process"),
+        assertEquals(Set.of("process"),
             streamsGroup.currentStandbyTaskProcessIds(fooSubtopology, 2));
-        assertEquals(Collections.singleton("process"),
+        assertEquals(Set.of("process"),
             streamsGroup.currentWarmupTaskProcessIds(fooSubtopology, 3));
         assertEquals("process", streamsGroup.currentActiveTaskProcessId(barSubtopology, 4));
-        assertEquals(Collections.singleton("process"),
+        assertEquals(Set.of("process"),
             streamsGroup.currentStandbyTaskProcessIds(barSubtopology, 5));
-        assertEquals(Collections.singleton("process"),
+        assertEquals(Set.of("process"),
             streamsGroup.currentWarmupTaskProcessIds(barSubtopology, 6));
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 7));
-        assertEquals(Collections.emptySet(),
+        assertEquals(Set.of(),
             streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
-        assertEquals(Collections.emptySet(),
+        assertEquals(Set.of(),
             streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
 
         member = new StreamsGroupMember.Builder(member)
@@ -257,19 +256,19 @@ public class StreamsGroupTest {
         streamsGroup.updateMember(member);
 
         assertEquals("process1", streamsGroup.currentActiveTaskProcessId(fooSubtopology, 1));
-        assertEquals(Collections.singleton("process1"),
+        assertEquals(Set.of("process1"),
             streamsGroup.currentStandbyTaskProcessIds(fooSubtopology, 2));
-        assertEquals(Collections.singleton("process1"),
+        assertEquals(Set.of("process1"),
             streamsGroup.currentWarmupTaskProcessIds(fooSubtopology, 3));
         assertEquals("process1", streamsGroup.currentActiveTaskProcessId(barSubtopology, 4));
-        assertEquals(Collections.singleton("process1"),
+        assertEquals(Set.of("process1"),
             streamsGroup.currentStandbyTaskProcessIds(barSubtopology, 5));
-        assertEquals(Collections.singleton("process1"),
+        assertEquals(Set.of("process1"),
             streamsGroup.currentWarmupTaskProcessIds(barSubtopology, 6));
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 7));
-        assertEquals(Collections.emptySet(),
+        assertEquals(Set.of(),
             streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
-        assertEquals(Collections.emptySet(),
+        assertEquals(Set.of(),
             streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
     }
 
@@ -284,9 +283,9 @@ public class StreamsGroupTest {
             .setProcessId("process")
             .setAssignedTasks(
                 new TasksTuple(
-                    emptyMap(),
+                    Map.of(),
-                    emptyMap(),
+                    Map.of(),
-                    emptyMap()
+                    Map.of()
                 )
             )
             .setTasksPendingRevocation(
@@ -329,8 +328,8 @@ public class StreamsGroupTest {
             .setAssignedTasks(
                 new TasksTuple(
                     mkTasksPerSubtopology(mkTasks(fooSubtopologyId, 1)),
-                    emptyMap(),
+                    Map.of(),
-                    emptyMap()
+                    Map.of()
                 )
             )
             .build();
@@ -342,8 +341,8 @@ public class StreamsGroupTest {
             .setAssignedTasks(
                 new TasksTuple(
                     mkTasksPerSubtopology(mkTasks(fooSubtopologyId, 1)),
-                    emptyMap(),
+                    Map.of(),
-                    emptyMap()
+                    Map.of()
                 )
             )
             .build();
@@ -436,26 +435,26 @@ public class StreamsGroupTest {
         streamsGroup.updateMember(member);
 
         assertEquals("process", streamsGroup.currentActiveTaskProcessId(fooSubtopology, 1));
-        assertEquals(Collections.singleton("process"), streamsGroup.currentStandbyTaskProcessIds(fooSubtopology, 2));
+        assertEquals(Set.of("process"), streamsGroup.currentStandbyTaskProcessIds(fooSubtopology, 2));
-        assertEquals(Collections.singleton("process"), streamsGroup.currentWarmupTaskProcessIds(fooSubtopology, 3));
+        assertEquals(Set.of("process"), streamsGroup.currentWarmupTaskProcessIds(fooSubtopology, 3));
         assertEquals("process", streamsGroup.currentActiveTaskProcessId(barSubtopology, 4));
-        assertEquals(Collections.singleton("process"), streamsGroup.currentStandbyTaskProcessIds(barSubtopology, 5));
+        assertEquals(Set.of("process"), streamsGroup.currentStandbyTaskProcessIds(barSubtopology, 5));
-        assertEquals(Collections.singleton("process"), streamsGroup.currentWarmupTaskProcessIds(barSubtopology, 6));
+        assertEquals(Set.of("process"), streamsGroup.currentWarmupTaskProcessIds(barSubtopology, 6));
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 7));
-        assertEquals(Collections.emptySet(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
+        assertEquals(Set.of(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
-        assertEquals(Collections.emptySet(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
+        assertEquals(Set.of(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
 
         streamsGroup.removeMember(member.memberId());
 
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 1));
-        assertEquals(Collections.emptySet(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 2));
+        assertEquals(Set.of(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 2));
-        assertEquals(Collections.emptySet(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 3));
+        assertEquals(Set.of(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 3));
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 3));
-        assertEquals(Collections.emptySet(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 4));
+        assertEquals(Set.of(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 4));
-        assertEquals(Collections.emptySet(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 5));
+        assertEquals(Set.of(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 5));
         assertNull(streamsGroup.currentActiveTaskProcessId(zarSubtopology, 7));
-        assertEquals(Collections.emptySet(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
+        assertEquals(Set.of(), streamsGroup.currentStandbyTaskProcessIds(zarSubtopology, 8));
-        assertEquals(Collections.emptySet(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
+        assertEquals(Set.of(), streamsGroup.currentWarmupTaskProcessIds(zarSubtopology, 9));
     }
 
     @Test
@@ -475,7 +474,7 @@ public class StreamsGroupTest {
         assertEquals(MemberState.STABLE, member1.state());
         assertEquals(StreamsGroup.StreamsGroupState.NOT_READY, streamsGroup.state());
 
-        streamsGroup.setTopology(new StreamsTopology(1, Collections.emptyMap()));
+        streamsGroup.setTopology(new StreamsTopology(1, Map.of()));
 
         assertEquals(MemberState.STABLE, member1.state());
         assertEquals(StreamsGroup.StreamsGroupState.ASSIGNING, streamsGroup.state());
@@ -672,7 +671,7 @@ public class StreamsGroupTest {
             mock(GroupCoordinatorMetricsShard.class)
         );
         group.setGroupEpoch(1);
-        group.setTopology(new StreamsTopology(1, Collections.emptyMap()));
+        group.setTopology(new StreamsTopology(1, Map.of()));
         group.setTargetAssignmentEpoch(1);
         group.updateMember(new StreamsGroupMember.Builder("member1")
             .setMemberEpoch(1)
@@ -737,7 +736,7 @@ public class StreamsGroupTest {
         assertEquals(StreamsGroup.StreamsGroupState.NOT_READY, streamsGroup.state());
         assertThrows(GroupNotEmptyException.class, streamsGroup::validateDeleteGroup);
 
-        streamsGroup.setTopology(new StreamsTopology(1, Collections.emptyMap()));
+        streamsGroup.setTopology(new StreamsTopology(1, Map.of()));
 
         assertEquals(StreamsGroup.StreamsGroupState.RECONCILING, streamsGroup.state());
         assertThrows(GroupNotEmptyException.class, streamsGroup::validateDeleteGroup);
@@ -781,7 +780,7 @@ public class StreamsGroupTest {
         assertEquals(StreamsGroup.StreamsGroupState.EMPTY.toString(), group.stateAsString(0));
 
         group.setGroupEpoch(1);
-        group.setTopology(new StreamsTopology(1, Collections.emptyMap()));
+        group.setTopology(new StreamsTopology(1, Map.of()));
         group.setTargetAssignmentEpoch(1);
         group.updateMember(new StreamsGroupMember.Builder("member1")
             .setMemberEpoch(1)
@@ -795,9 +794,9 @@ public class StreamsGroupTest {
             .setTopologyEpoch(1)
             .setProcessId("process1")
             .setUserEndpoint(new StreamsGroupMemberMetadataValue.Endpoint().setHost("host1").setPort(9092))
-            .setClientTags(Collections.singletonMap("tag1", "value1"))
+            .setClientTags(Map.of("tag1", "value1"))
-            .setAssignedTasks(new TasksTuple(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap()))
+            .setAssignedTasks(new TasksTuple(Map.of(), Map.of(), Map.of()))
-            .setTasksPendingRevocation(new TasksTuple(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap()))
+            .setTasksPendingRevocation(new TasksTuple(Map.of(), Map.of(), Map.of()))
             .build());
         group.updateMember(new StreamsGroupMember.Builder("member2")
             .setMemberEpoch(1)
@@ -811,9 +810,9 @@ public class StreamsGroupTest {
             .setTopologyEpoch(1)
             .setProcessId("process2")
             .setUserEndpoint(new StreamsGroupMemberMetadataValue.Endpoint().setHost("host2").setPort(9092))
-            .setClientTags(Collections.singletonMap("tag2", "value2"))
+            .setClientTags(Map.of("tag2", "value2"))
-            .setAssignedTasks(new TasksTuple(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap()))
+            .setAssignedTasks(new TasksTuple(Map.of(), Map.of(), Map.of()))
-            .setTasksPendingRevocation(new TasksTuple(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap()))
+            .setTasksPendingRevocation(new TasksTuple(Map.of(), Map.of(), Map.of()))
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
 
@@ -821,7 +820,7 @@ public class StreamsGroupTest {
             .setGroupId("group-id-1")
             .setGroupState(StreamsGroup.StreamsGroupState.STABLE.toString())
             .setGroupEpoch(1)
-            .setTopology(new StreamsGroupDescribeResponseData.Topology().setEpoch(1).setSubtopologies(Collections.emptyList()))
+            .setTopology(new StreamsGroupDescribeResponseData.Topology().setEpoch(1).setSubtopologies(List.of()))
             .setAssignmentEpoch(1)
             .setMembers(Arrays.asList(
                 new StreamsGroupDescribeResponseData.Member()
@@ -834,7 +833,7 @@ public class StreamsGroupTest {
                     .setTopologyEpoch(1)
                     .setProcessId("process1")
                     .setUserEndpoint(new StreamsGroupDescribeResponseData.Endpoint().setHost("host1").setPort(9092))
-                    .setClientTags(Collections.singletonList(new StreamsGroupDescribeResponseData.KeyValue().setKey("tag1").setValue("value1")))
+                    .setClientTags(List.of(new StreamsGroupDescribeResponseData.KeyValue().setKey("tag1").setValue("value1")))
                     .setAssignment(new StreamsGroupDescribeResponseData.Assignment())
                     .setTargetAssignment(new StreamsGroupDescribeResponseData.Assignment()),
                 new StreamsGroupDescribeResponseData.Member()
@@ -847,7 +846,7 @@ public class StreamsGroupTest {
                     .setTopologyEpoch(1)
                     .setProcessId("process2")
                     .setUserEndpoint(new StreamsGroupDescribeResponseData.Endpoint().setHost("host2").setPort(9092))
-                    .setClientTags(Collections.singletonList(new StreamsGroupDescribeResponseData.KeyValue().setKey("tag2").setValue("value2")))
+                    .setClientTags(List.of(new StreamsGroupDescribeResponseData.KeyValue().setKey("tag2").setValue("value2")))
                     .setAssignment(new StreamsGroupDescribeResponseData.Assignment())
                     .setTargetAssignment(new StreamsGroupDescribeResponseData.Assignment())
             ));
@@ -861,20 +860,20 @@ public class StreamsGroupTest {
         SnapshotRegistry snapshotRegistry = new SnapshotRegistry(LOG_CONTEXT);
         GroupCoordinatorMetricsShard metricsShard = new GroupCoordinatorMetricsShard(
             snapshotRegistry,
-            emptyMap(),
+            Map.of(),
             new TopicPartition("__consumer_offsets", 0)
         );
         StreamsGroup group = new StreamsGroup(LOG_CONTEXT, snapshotRegistry, "group-foo", metricsShard);
         snapshotRegistry.idempotentCreateSnapshot(0);
-        assertTrue(group.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(group.isInStates(Set.of("empty"), 0));
-        assertFalse(group.isInStates(Collections.singleton("Empty"), 0));
+        assertFalse(group.isInStates(Set.of("Empty"), 0));
 
         group.updateMember(new StreamsGroupMember.Builder("member1")
             .build());
         snapshotRegistry.idempotentCreateSnapshot(1);
-        assertTrue(group.isInStates(Collections.singleton("empty"), 0));
+        assertTrue(group.isInStates(Set.of("empty"), 0));
-        assertTrue(group.isInStates(Collections.singleton("not_ready"), 1));
+        assertTrue(group.isInStates(Set.of("not_ready"), 1));
-        assertFalse(group.isInStates(Collections.singleton("empty"), 1));
+        assertFalse(group.isInStates(Set.of("empty"), 1));
     }
 
     @Test
@@ -883,7 +882,7 @@ public class StreamsGroupTest {
         GroupCoordinatorMetricsShard metricsShard = mock(GroupCoordinatorMetricsShard.class);
         StreamsGroup streamsGroup = new StreamsGroup(LOG_CONTEXT, snapshotRegistry, "test-group", metricsShard);
 
-        StreamsTopology topology = new StreamsTopology(1, Collections.emptyMap());
+        StreamsTopology topology = new StreamsTopology(1, Map.of());
 
         ConfiguredTopology topo = mock(ConfiguredTopology.class);
         when(topo.isReady()).thenReturn(true);
@@ -925,7 +924,7 @@ public class StreamsGroupTest {
         assertTrue(streamsGroup.configuredTopology().isEmpty(), "Configured topology should not be present");
         assertEquals(partitionMetadata, streamsGroup.partitionMetadata());
 
-        StreamsTopology topology = new StreamsTopology(1, Collections.emptyMap());
+        StreamsTopology topology = new StreamsTopology(1, Map.of());
         ConfiguredTopology topo = mock(ConfiguredTopology.class);
         when(topo.isReady()).thenReturn(true);
         try (MockedStatic<InternalTopicManager> mocked = mockStatic(InternalTopicManager.class)) {
@@ -955,7 +954,7 @@ public class StreamsGroupTest {
         assertTrue(streamsGroup.configuredTopology().isEmpty(), "Configured topology should not be present");
         assertEquals(partitionMetadata, streamsGroup.partitionMetadata());
 
-        StreamsTopology topology = new StreamsTopology(1, Collections.emptyMap());
+        StreamsTopology topology = new StreamsTopology(1, Map.of());
         streamsGroup.setTopology(topology);
         ConfiguredTopology topo = mock(ConfiguredTopology.class);
         when(topo.isReady()).thenReturn(true);
@@ -995,7 +994,7 @@ public class StreamsGroupTest {
         when(topicImage.partitions()).thenReturn(Collections.singletonMap(0, null));
         when(topicsImage.getTopic("topic1")).thenReturn(topicImage);
         StreamsTopology topology = mock(StreamsTopology.class);
-        when(topology.requiredTopics()).thenReturn(Collections.singleton("topic1"));
+        when(topology.requiredTopics()).thenReturn(Set.of("topic1"));
 
         Map<String, TopicMetadata> partitionMetadata = streamsGroup.computePartitionMetadata(topicsImage, topology);
 

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/TargetAssignmentBuilderTest.java

@@ -33,7 +33,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.EnumSource;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -74,12 +73,12 @@ public class TargetAssignmentBuilderTest {
 
         TargetAssignmentBuilder.TargetAssignmentResult result = builder.build();
 
-        List<CoordinatorRecord> expectedRecords = Collections.singletonList(
+        List<CoordinatorRecord> expectedRecords = List.of(
             StreamsCoordinatorRecordHelpers.newStreamsGroupTargetAssignmentEpochRecord(groupId, groupEpoch)
         );
 
         assertEquals(expectedRecords, result.records());
-        assertEquals(Collections.emptyMap(), result.targetAssignment());
+        assertEquals(Map.of(), result.targetAssignment());
     }
 
     @ParameterizedTest

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/TasksTupleTest.java

@@ -22,7 +22,6 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -42,9 +41,9 @@ public class TasksTupleTest {
 
     @Test
     public void testTasksCannotBeNull() {
-        assertThrows(NullPointerException.class, () -> new TasksTuple(null, Collections.emptyMap(), Collections.emptyMap()));
+        assertThrows(NullPointerException.class, () -> new TasksTuple(null, Map.of(), Map.of()));
-        assertThrows(NullPointerException.class, () -> new TasksTuple(Collections.emptyMap(), null, Collections.emptyMap()));
+        assertThrows(NullPointerException.class, () -> new TasksTuple(Map.of(), null, Map.of()));
-        assertThrows(NullPointerException.class, () -> new TasksTuple(Collections.emptyMap(), Collections.emptyMap(), null));
+        assertThrows(NullPointerException.class, () -> new TasksTuple(Map.of(), Map.of(), null));
     }
 
     @Test
@@ -61,11 +60,11 @@ public class TasksTupleTest {
         TasksTuple tuple = new TasksTuple(activeTasks, standbyTasks, warmupTasks);
 
         assertEquals(activeTasks, tuple.activeTasks());
-        assertThrows(UnsupportedOperationException.class, () -> tuple.activeTasks().put("not allowed", Collections.emptySet()));
+        assertThrows(UnsupportedOperationException.class, () -> tuple.activeTasks().put("not allowed", Set.of()));
         assertEquals(standbyTasks, tuple.standbyTasks());
-        assertThrows(UnsupportedOperationException.class, () -> tuple.standbyTasks().put("not allowed", Collections.emptySet()));
+        assertThrows(UnsupportedOperationException.class, () -> tuple.standbyTasks().put("not allowed", Set.of()));
         assertEquals(warmupTasks, tuple.warmupTasks());
-        assertThrows(UnsupportedOperationException.class, () -> tuple.warmupTasks().put("not allowed", Collections.emptySet()));
+        assertThrows(UnsupportedOperationException.class, () -> tuple.warmupTasks().put("not allowed", Set.of()));
     }
 
     @Test

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/assignor/GroupSpecImplTest.java

@@ -19,7 +19,6 @@ package org.apache.kafka.coordinator.group.streams.assignor;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -39,13 +38,13 @@ public class GroupSpecImplTest {
         members.put("test-member", new AssignmentMemberSpec(
             Optional.of("test-instance"),
             Optional.of("test-rack"),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         ));
 
         groupSpec = new GroupSpecImpl(

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/assignor/MockAssignorTest.java

@@ -18,7 +18,6 @@ package org.apache.kafka.coordinator.group.streams.assignor;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -43,10 +42,10 @@ public class MockAssignorTest {
 
         TaskAssignorException ex = assertThrows(TaskAssignorException.class, () -> assignor.assign(
             new GroupSpecImpl(
-                Collections.emptyMap(),
+                Map.of(),
                 new HashMap<>()
             ),
-            new TopologyDescriberImpl(5, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(5, List.of("test-subtopology"))
         ));
 
         assertEquals("No member available to assign task 0 of subtopology test-subtopology", ex.getMessage());
@@ -58,25 +57,25 @@ public class MockAssignorTest {
         final AssignmentMemberSpec memberSpec1 = new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.singletonMap("test-subtopology", new HashSet<>(List.of(0))),
+            Map.of("test-subtopology", new HashSet<>(List.of(0))),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         final AssignmentMemberSpec memberSpec2 = new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.singletonMap("test-subtopology", new HashSet<>(List.of(0))),
+            Map.of("test-subtopology", new HashSet<>(List.of(0))),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         TaskAssignorException ex = assertThrows(TaskAssignorException.class, () -> assignor.assign(
@@ -84,7 +83,7 @@ public class MockAssignorTest {
                 Map.of("member1", memberSpec1, "member2", memberSpec2),
                 new HashMap<>()
             ),
-            new TopologyDescriberImpl(5, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(5, List.of("test-subtopology"))
         ));
 
         assertEquals("Task 0 of subtopology test-subtopology is assigned to multiple members", ex.getMessage());
@@ -95,10 +94,10 @@ public class MockAssignorTest {
 
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(
-                Collections.emptyMap(),
+                Map.of(),
                 new HashMap<>()
             ),
-            new TopologyDescriberImpl(5, Collections.emptyList())
+            new TopologyDescriberImpl(5, List.of())
         );
 
         assertEquals(0, result.members().size());
@@ -111,18 +110,18 @@ public class MockAssignorTest {
         final AssignmentMemberSpec memberSpec = new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(
-                Collections.singletonMap("test_member", memberSpec),
+                Map.of("test_member", memberSpec),
                 new HashMap<>()
             ),
             new TopologyDescriberImpl(4, List.of("test-subtopology"))
@@ -143,25 +142,25 @@ public class MockAssignorTest {
         final AssignmentMemberSpec memberSpec1 = new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         final AssignmentMemberSpec memberSpec2 = new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         final GroupAssignment result = assignor.assign(
@@ -200,12 +199,12 @@ public class MockAssignorTest {
                 mkEntry("test-subtopology1", new HashSet<>(List.of(0, 2, 3))),
                 mkEntry("test-subtopology2", new HashSet<>(List.of(0)))
             ),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
 
         final AssignmentMemberSpec memberSpec2 = new AssignmentMemberSpec(
@@ -215,12 +214,12 @@ public class MockAssignorTest {
                 mkEntry("test-subtopology1", new HashSet<>(List.of(1))),
                 mkEntry("test-subtopology2", new HashSet<>(List.of(3)))
             ),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             "test-process",
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap()
+            Map.of()
         );
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignorTest.java

@@ -22,7 +22,6 @@ import org.mockito.internal.util.collections.Sets;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -59,7 +58,7 @@ public class StickyTaskAssignorTest {
                 mkMap(mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3)),
                 new HashMap<>()
             ),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         assertEquals(3, result.members().size());
@@ -132,13 +131,13 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldNotMigrateActiveTaskToOtherProcess() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Collections.singleton(0))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Set.of(0))), Map.of());
-        AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
         Map<String, AssignmentMemberSpec> members = mkMap(mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
@@ -151,13 +150,13 @@ public class StickyTaskAssignorTest {
             testMember1.activeTasks().get("test-subtopology").size() + testMember2.activeTasks().get("test-subtopology").size());
 
         // flip the previous active tasks assignment around.
-        memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Collections.singleton(2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Set.of(2))), Map.of());
         members = mkMap(mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3));
 
         result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         testMember2 = result.members().get("member2");
@@ -172,15 +171,15 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldMigrateActiveTasksToNewProcessWithoutChangingAllAssignments() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 2))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
         final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3");
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
@@ -208,7 +207,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
@@ -227,7 +226,7 @@ public class StickyTaskAssignorTest {
         final Map<String, Set<Integer>> activeTasks = mkMap(
             mkEntry("test-subtopology1", Sets.newSet(0, 1, 2, 3, 4, 5)),
             mkEntry("test-subtopology2", Sets.newSet(0)));
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", activeTasks, Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", activeTasks, Map.of());
         final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2");
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2));
@@ -254,9 +253,9 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldKeepActiveTaskStickinessWhenMoreClientThanActiveTasks() {
-        AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Collections.singleton(0))), Collections.emptyMap());
+        AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Set.of(0))), Map.of());
-        AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(2))), Collections.emptyMap());
+        AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(2))), Map.of());
-        AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
         AssignmentMemberSpec memberSpec4 = createAssignmentMemberSpec("process4");
         AssignmentMemberSpec memberSpec5 = createAssignmentMemberSpec("process5");
         Map<String, AssignmentMemberSpec> members = mkMap(
@@ -265,21 +264,21 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
         assertNotNull(testMember1);
         assertEquals(1, testMember1.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember1.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember1.activeTasks().get("test-subtopology"));
         MemberAssignment testMember2 = result.members().get("member2");
         assertNotNull(testMember2);
         assertEquals(1, testMember2.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(2), testMember2.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(2), testMember2.activeTasks().get("test-subtopology"));
         MemberAssignment testMember3 = result.members().get("member3");
         assertNotNull(testMember3);
         assertEquals(1, testMember3.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember3.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember3.activeTasks().get("test-subtopology"));
         MemberAssignment testMember4 = result.members().get("member4");
         assertNotNull(testMember4);
         assertNull(testMember4.activeTasks().get("test-subtopology"));
@@ -289,17 +288,17 @@ public class StickyTaskAssignorTest {
 
         // change up the assignment and make sure it is still sticky
         memberSpec1 = createAssignmentMemberSpec("process1");
-        memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(0))), Collections.emptyMap());
+        memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(0))), Map.of());
         memberSpec3 = createAssignmentMemberSpec("process3");
-        memberSpec4 = createAssignmentMemberSpec("process4", mkMap(mkEntry("test-subtopology", Collections.singleton(2))), Collections.emptyMap());
+        memberSpec4 = createAssignmentMemberSpec("process4", mkMap(mkEntry("test-subtopology", Set.of(2))), Map.of());
-        memberSpec5 = createAssignmentMemberSpec("process5", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        memberSpec5 = createAssignmentMemberSpec("process5", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
         members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2),
             mkEntry("member3", memberSpec3), mkEntry("member4", memberSpec4), mkEntry("member5", memberSpec5));
 
         result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         testMember1 = result.members().get("member1");
@@ -308,113 +307,113 @@ public class StickyTaskAssignorTest {
         testMember2 = result.members().get("member2");
         assertNotNull(testMember2);
         assertEquals(1, testMember2.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember2.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember2.activeTasks().get("test-subtopology"));
         testMember3 = result.members().get("member3");
         assertNotNull(testMember3);
         assertNull(testMember3.activeTasks().get("test-subtopology"));
         testMember4 = result.members().get("member4");
         assertNotNull(testMember4);
         assertEquals(1, testMember4.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(2), testMember4.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(2), testMember4.activeTasks().get("test-subtopology"));
         testMember5 = result.members().get("member5");
         assertNotNull(testMember5);
         assertEquals(1, testMember5.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember5.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember5.activeTasks().get("test-subtopology"));
     }
 
     @Test
     public void shouldAssignTasksToClientWithPreviousStandbyTasks() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Collections.singleton(2))));
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", Map.of(), mkMap(mkEntry("test-subtopology", Set.of(2))));
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Collections.singleton(1))));
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Map.of(), mkMap(mkEntry("test-subtopology", Set.of(1))));
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Collections.singleton(0))));
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", Map.of(), mkMap(mkEntry("test-subtopology", Set.of(0))));
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
         assertNotNull(testMember1);
         assertEquals(1, testMember1.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(2), testMember1.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(2), testMember1.activeTasks().get("test-subtopology"));
         MemberAssignment testMember2 = result.members().get("member2");
         assertNotNull(testMember2);
         assertEquals(1, testMember2.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember2.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember2.activeTasks().get("test-subtopology"));
         MemberAssignment testMember3 = result.members().get("member3");
         assertNotNull(testMember3);
         assertEquals(1, testMember3.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember3.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember3.activeTasks().get("test-subtopology"));
     }
 
     @Test
     public void shouldNotAssignStandbyTasksToClientWithPreviousStandbyTasksAndCurrentActiveTasks() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Collections.singleton(0))));
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", Map.of(), mkMap(mkEntry("test-subtopology", Set.of(0))));
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Collections.singleton(1))));
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Map.of(), mkMap(mkEntry("test-subtopology", Set.of(1))));
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(2, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(2, true, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
         assertNotNull(testMember1);
         assertEquals(1, testMember1.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember1.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember1.activeTasks().get("test-subtopology"));
         assertEquals(1, testMember1.standbyTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember1.standbyTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember1.standbyTasks().get("test-subtopology"));
         MemberAssignment testMember2 = result.members().get("member2");
         assertNotNull(testMember2);
         assertEquals(1, testMember2.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember2.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember2.activeTasks().get("test-subtopology"));
         assertEquals(1, testMember2.standbyTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember2.standbyTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember2.standbyTasks().get("test-subtopology"));
     }
 
     @Test
     public void shouldAssignBasedOnCapacityWhenMultipleClientHaveStandbyTasks() {
         final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1",
-            mkMap(mkEntry("test-subtopology", Collections.singleton(0))),
+            mkMap(mkEntry("test-subtopology", Set.of(0))),
-            mkMap(mkEntry("test-subtopology", Collections.singleton(1))));
+            mkMap(mkEntry("test-subtopology", Set.of(1))));
         final AssignmentMemberSpec memberSpec21 = createAssignmentMemberSpec("process2",
-            mkMap(mkEntry("test-subtopology", Collections.singleton(2))),
+            mkMap(mkEntry("test-subtopology", Set.of(2))),
-            mkMap(mkEntry("test-subtopology", Collections.singleton(1))));
+            mkMap(mkEntry("test-subtopology", Set.of(1))));
         final AssignmentMemberSpec memberSpec22 = createAssignmentMemberSpec("process2",
-            Collections.emptyMap(), Collections.emptyMap());
+            Map.of(), Map.of());
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1),
             mkEntry("member2_1", memberSpec21), mkEntry("member2_2", memberSpec22));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         MemberAssignment testMember1 = result.members().get("member1");
         assertNotNull(testMember1);
         assertEquals(1, testMember1.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(0), testMember1.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(0), testMember1.activeTasks().get("test-subtopology"));
         MemberAssignment testMember21 = result.members().get("member2_1");
         assertNotNull(testMember21);
         assertEquals(1, testMember21.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(2), testMember21.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(2), testMember21.activeTasks().get("test-subtopology"));
         MemberAssignment testMember22 = result.members().get("member2_2");
         assertNotNull(testMember22);
         assertEquals(1, testMember22.activeTasks().get("test-subtopology").size());
-        assertEquals(Collections.singleton(1), testMember22.activeTasks().get("test-subtopology"));
+        assertEquals(Set.of(1), testMember22.activeTasks().get("test-subtopology"));
     }
 
     @Test
     public void shouldAssignStandbyTasksToDifferentClientThanCorrespondingActiveTaskIsAssignedTo() {
         final Map<String, Set<Integer>> tasks = mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 3)));
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Collections.singleton(0))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Set.of(0))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Collections.singleton(2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Set.of(2))), Map.of());
-        final AssignmentMemberSpec memberSpec4 = createAssignmentMemberSpec("process4", mkMap(mkEntry("test-subtopology", Collections.singleton(3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec4 = createAssignmentMemberSpec("process4", mkMap(mkEntry("test-subtopology", Set.of(3))), Map.of());
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2),
             mkEntry("member3", memberSpec3), mkEntry("member4", memberSpec4));
@@ -422,7 +421,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(4, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, true, List.of("test-subtopology"))
         );
 
         final List<Integer> member1TaskIds = getAllStandbyTaskIds(result, "member1");
@@ -448,9 +447,9 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldAssignMultipleReplicasOfStandbyTask() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Collections.singleton(0))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Set.of(0))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Collections.singleton(1))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Set.of(1))), Map.of());
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Collections.singleton(2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Set.of(2))), Map.of());
         Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2),
             mkEntry("member3", memberSpec3));
@@ -458,7 +457,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "2"))),
-            new TopologyDescriberImpl(3, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, true, List.of("test-subtopology"))
         );
 
         assertEquals(Sets.newSet(1, 2), new HashSet<>(getAllStandbyTaskIds(result, "member1")));
@@ -475,7 +474,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(1, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(1, true, List.of("test-subtopology"))
         );
 
         assertTrue(getAllStandbyTasks(result, "member1").isEmpty());
@@ -493,7 +492,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(3, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, true, List.of("test-subtopology"))
         );
 
         assertEquals(Sets.newSet(0, 1, 2), new HashSet<>(getAllActiveTaskIds(result)));
@@ -513,7 +512,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskIds(result, "member1_1", "member1_2", "member1_3").size());
@@ -535,7 +534,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         assertEquals(3, getAllActiveTaskIds(result, "member1", "member2", "member3", "member4", "member5", "member6").size());
@@ -557,7 +556,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(3, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, true, List.of("test-subtopology"))
         );
 
         for (String memberId : result.members().keySet()) {
@@ -595,7 +594,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(4, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, true, List.of("test-subtopology"))
         );
 
         for (final String memberId : allMemberIds) {
@@ -610,9 +609,9 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldNotHaveSameAssignmentOnAnyTwoHostsWhenThereArePreviousActiveTasks() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(1, 2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(1, 2))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(3))), Map.of());
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0))), Map.of());
         final AssignmentMemberSpec memberSpec4 = createAssignmentMemberSpec("process4");
         final List<String> allMemberIds = asList("member1", "member2", "member3", "member4");
         Map<String, AssignmentMemberSpec> members = mkMap(
@@ -621,7 +620,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(4, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, true, List.of("test-subtopology"))
         );
 
         for (final String memberId : allMemberIds) {
@@ -649,7 +648,7 @@ public class StickyTaskAssignorTest {
         final GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members,
                 mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, "1"))),
-            new TopologyDescriberImpl(4, true, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, true, List.of("test-subtopology"))
         );
 
         for (final String memberId : allMemberIds) {
@@ -664,7 +663,7 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldReBalanceTasksAcrossAllClientsWhenCapacityAndTaskCountTheSame() {
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 3))), Map.of());
         final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1");
         final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2");
         final AssignmentMemberSpec memberSpec4 = createAssignmentMemberSpec("process4");
@@ -673,7 +672,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(4, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskCount(result, "member1"));
@@ -684,7 +683,7 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldReBalanceTasksAcrossClientsWhenCapacityLessThanTaskCount() {
-        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 3))), Map.of());
         final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1");
         final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2");
         Map<String, AssignmentMemberSpec> members = mkMap(
@@ -692,7 +691,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(4, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskCount(result, "member1"));
@@ -702,7 +701,7 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldRebalanceTasksToClientsBasedOnCapacity() {
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 3, 2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 3, 2))), Map.of());
         final AssignmentMemberSpec memberSpec31 = createAssignmentMemberSpec("process3");
         final AssignmentMemberSpec memberSpec32 = createAssignmentMemberSpec("process3");
         Map<String, AssignmentMemberSpec> members = mkMap(
@@ -710,7 +709,7 @@ public class StickyTaskAssignorTest {
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(3, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(3, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskCount(result, "member2"));
@@ -721,15 +720,15 @@ public class StickyTaskAssignorTest {
     public void shouldMoveMinimalNumberOfTasksWhenPreviouslyAboveCapacityAndNewClientAdded() {
         final Set<Integer> p1PrevTasks = Sets.newSet(0, 2);
         final Set<Integer> p2PrevTasks = Sets.newSet(1, 3);
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", p1PrevTasks)), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", p1PrevTasks)), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", p2PrevTasks)), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", p2PrevTasks)), Map.of());
         final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3");
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(4, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(4, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskCount(result, "member3"));
@@ -743,14 +742,14 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldNotMoveAnyTasksWhenNewTasksAdded() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(2, 3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(2, 3))), Map.of());
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(6, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(6, false, List.of("test-subtopology"))
         );
 
         final List<Integer> mem1Tasks = getAllActiveTaskIds(result, "member1");
@@ -763,15 +762,15 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldAssignNewTasksToNewClientWhenPreviousTasksAssignedToOldClients() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(2, 1))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(2, 1))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 3))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 3))), Map.of());
         final AssignmentMemberSpec memberSpec3 = createAssignmentMemberSpec("process3");
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(6, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(6, false, List.of("test-subtopology"))
         );
 
         final List<Integer> mem1Tasks = getAllActiveTaskIds(result, "member1");
@@ -797,7 +796,7 @@ public class StickyTaskAssignorTest {
             mkMap(mkEntry("test-subtopology2", Sets.newSet(0, 1, 3))),
             mkMap(mkEntry("test-subtopology0", Sets.newSet(2)), mkEntry("test-subtopology1", Sets.newSet(2))));
         final AssignmentMemberSpec newMemberSpec = createAssignmentMemberSpec("process4",
-            Collections.emptyMap(),
+            Map.of(),
             mkMap(mkEntry("test-subtopology0", Sets.newSet(0, 1, 2, 3)), mkEntry("test-subtopology1", Sets.newSet(0, 1, 2, 3)), mkEntry("test-subtopology2", Sets.newSet(0, 1, 2, 3))));
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("member3", memberSpec3), mkEntry("newMember", newMemberSpec));
@@ -826,10 +825,10 @@ public class StickyTaskAssignorTest {
             mkMap(mkEntry("test-subtopology0", Sets.newSet(0)), mkEntry("test-subtopology1", Sets.newSet(1)), mkEntry("test-subtopology2", Sets.newSet(2))),
             mkMap(mkEntry("test-subtopology0", Sets.newSet(1, 2, 3)), mkEntry("test-subtopology1", Sets.newSet(0, 2, 3)), mkEntry("test-subtopology2", Sets.newSet(0, 1, 3))));
         final AssignmentMemberSpec bounce1 = createAssignmentMemberSpec("bounce1",
-            Collections.emptyMap(),
+            Map.of(),
             mkMap(mkEntry("test-subtopology2", Sets.newSet(0, 1, 3))));
         final AssignmentMemberSpec bounce2 = createAssignmentMemberSpec("bounce2",
-            Collections.emptyMap(),
+            Map.of(),
             mkMap(mkEntry("test-subtopology0", Sets.newSet(2, 3)), mkEntry("test-subtopology1", Sets.newSet(0))));
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("bounce_member1", bounce1), mkEntry("bounce_member2", bounce2));
@@ -851,14 +850,14 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldAssignTasksToNewClient() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(1, 2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(1, 2))), Map.of());
         final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2");
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(2, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(2, false, List.of("test-subtopology"))
         );
 
         assertEquals(1, getAllActiveTaskCount(result, "member1"));
@@ -866,15 +865,15 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldAssignTasksToNewClientWithoutFlippingAssignmentBetweenExistingClients() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(3, 4, 5))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", mkMap(mkEntry("test-subtopology", Sets.newSet(3, 4, 5))), Map.of());
         final AssignmentMemberSpec newMemberSpec = createAssignmentMemberSpec("process3");
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("newMember", newMemberSpec));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(6, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(6, false, List.of("test-subtopology"))
         );
 
         final List<Integer> mem1Tasks = getAllActiveTaskIds(result, "member1");
@@ -892,15 +891,15 @@ public class StickyTaskAssignorTest {
 
     @Test
     public void shouldAssignTasksToNewClientWithoutFlippingAssignmentBetweenExistingAndBouncedClients() {
-        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 6))), Collections.emptyMap());
+        final AssignmentMemberSpec memberSpec1 = createAssignmentMemberSpec("process1", mkMap(mkEntry("test-subtopology", Sets.newSet(0, 1, 2, 6))), Map.of());
-        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Collections.emptyMap(), mkMap(mkEntry("test-subtopology", Sets.newSet(3, 4, 5))));
+        final AssignmentMemberSpec memberSpec2 = createAssignmentMemberSpec("process2", Map.of(), mkMap(mkEntry("test-subtopology", Sets.newSet(3, 4, 5))));
         final AssignmentMemberSpec newMemberSpec = createAssignmentMemberSpec("newProcess");
         final Map<String, AssignmentMemberSpec> members = mkMap(
             mkEntry("member1", memberSpec1), mkEntry("member2", memberSpec2), mkEntry("newMember", newMemberSpec));
 
         GroupAssignment result = assignor.assign(
             new GroupSpecImpl(members, new HashMap<>()),
-            new TopologyDescriberImpl(7, false, Collections.singletonList("test-subtopology"))
+            new TopologyDescriberImpl(7, false, List.of("test-subtopology"))
         );
 
         final List<Integer> mem1Tasks = getAllActiveTaskIds(result, "member1");
@@ -1054,13 +1053,13 @@ public class StickyTaskAssignorTest {
         return new AssignmentMemberSpec(
             Optional.empty(),
             Optional.empty(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
             processId,
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap());
+            Map.of());
     }
 
     private AssignmentMemberSpec createAssignmentMemberSpec(final String processId, final Map<String, Set<Integer>> prevActiveTasks,
@@ -1070,11 +1069,11 @@ public class StickyTaskAssignorTest {
             Optional.empty(),
             prevActiveTasks,
             prevStandbyTasks,
-            Collections.emptyMap(),
+            Map.of(),
             processId,
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap(),
+            Map.of(),
-            Collections.emptyMap());
+            Map.of());
     }
 
     static class TopologyDescriberImpl implements TopologyDescriber {

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/ChangelogTopicsTest.java

@@ -24,7 +24,6 @@ import org.apache.kafka.coordinator.group.generated.StreamsGroupTopologyValue.To
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.OptionalInt;
@@ -46,23 +45,23 @@ public class ChangelogTopicsTest {
         .setTopicConfigs(List.of(TOPIC_CONFIG));
     private static final Subtopology SUBTOPOLOGY_NO_SOURCE = new Subtopology()
         .setSubtopologyId("SUBTOPOLOGY_NO_SOURCE")
-        .setSourceTopics(Collections.emptyList())
+        .setSourceTopics(List.of())
-        .setRepartitionSinkTopics(Collections.singletonList(SINK_TOPIC_NAME))
+        .setRepartitionSinkTopics(List.of(SINK_TOPIC_NAME))
         .setRepartitionSourceTopics(List.of(REPARTITION_TOPIC_INFO))
-        .setStateChangelogTopics(Collections.emptyList());
+        .setStateChangelogTopics(List.of());
     private static final Subtopology SUBTOPOLOGY_STATELESS = new Subtopology()
         .setSubtopologyId("SUBTOPOLOGY_STATELESS")
-        .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_NAME))
+        .setSourceTopics(List.of(SOURCE_TOPIC_NAME))
-        .setRepartitionSinkTopics(Collections.singletonList(SINK_TOPIC_NAME))
+        .setRepartitionSinkTopics(List.of(SINK_TOPIC_NAME))
         .setRepartitionSourceTopics(List.of(REPARTITION_TOPIC_INFO))
-        .setStateChangelogTopics(Collections.emptyList());
+        .setStateChangelogTopics(List.of());
     private static final TopicInfo SOURCE_CHANGELOG_TOPIC_CONFIG = new TopicInfo()
         .setName(SOURCE_TOPIC_NAME)
         .setTopicConfigs(List.of(TOPIC_CONFIG));
     private static final Subtopology SUBTOPOLOGY_SOURCE_CHANGELOG = new Subtopology()
         .setSubtopologyId("SUBTOPOLOGY_SOURCE_CHANGELOG")
-        .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_NAME))
+        .setSourceTopics(List.of(SOURCE_TOPIC_NAME))
-        .setRepartitionSinkTopics(Collections.singletonList(SINK_TOPIC_NAME))
+        .setRepartitionSinkTopics(List.of(SINK_TOPIC_NAME))
         .setRepartitionSourceTopics(List.of(REPARTITION_TOPIC_INFO))
         .setStateChangelogTopics(List.of(SOURCE_CHANGELOG_TOPIC_CONFIG));
     private static final TopicInfo CHANGELOG_TOPIC_CONFIG = new TopicInfo()
@@ -70,14 +69,14 @@ public class ChangelogTopicsTest {
         .setTopicConfigs(List.of(TOPIC_CONFIG));
     private static final Subtopology SUBTOPOLOGY_STATEFUL = new Subtopology()
         .setSubtopologyId("SUBTOPOLOGY_STATEFUL")
-        .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_NAME))
+        .setSourceTopics(List.of(SOURCE_TOPIC_NAME))
-        .setRepartitionSinkTopics(Collections.singletonList(SINK_TOPIC_NAME))
+        .setRepartitionSinkTopics(List.of(SINK_TOPIC_NAME))
         .setRepartitionSourceTopics(List.of(REPARTITION_TOPIC_INFO))
         .setStateChangelogTopics(List.of(CHANGELOG_TOPIC_CONFIG));
     private static final Subtopology SUBTOPOLOGY_BOTH = new Subtopology()
         .setSubtopologyId("SUBTOPOLOGY_BOTH")
-        .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_NAME))
+        .setSourceTopics(List.of(SOURCE_TOPIC_NAME))
-        .setRepartitionSinkTopics(Collections.singletonList(SINK_TOPIC_NAME))
+        .setRepartitionSinkTopics(List.of(SINK_TOPIC_NAME))
         .setRepartitionSourceTopics(List.of(REPARTITION_TOPIC_INFO))
         .setStateChangelogTopics(List.of(SOURCE_CHANGELOG_TOPIC_CONFIG, CHANGELOG_TOPIC_CONFIG));
 
@@ -104,7 +103,7 @@ public class ChangelogTopicsTest {
             new ChangelogTopics(LOG_CONTEXT, subtopologies, ChangelogTopicsTest::topicPartitionProvider);
         Map<String, Integer> setup = changelogTopics.setup();
 
-        assertEquals(Collections.emptyMap(), setup);
+        assertEquals(Map.of(), setup);
     }
 
     @Test
@@ -126,7 +125,7 @@ public class ChangelogTopicsTest {
             new ChangelogTopics(LOG_CONTEXT, subtopologies, ChangelogTopicsTest::topicPartitionProvider);
         Map<String, Integer> setup = changelogTopics.setup();
 
-        assertEquals(Collections.emptyMap(), setup);
+        assertEquals(Map.of(), setup);
     }
 
     @Test

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredInternalTopicTest.java

@@ -21,7 +21,6 @@ import org.apache.kafka.common.message.StreamsGroupDescribeResponseData;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -34,13 +33,13 @@ public class ConfiguredInternalTopicTest {
     @Test
     public void testConstructorWithNullName() {
         assertThrows(NullPointerException.class,
-            () -> new ConfiguredInternalTopic(null, 1, Optional.empty(), Collections.emptyMap()));
+            () -> new ConfiguredInternalTopic(null, 1, Optional.empty(), Map.of()));
     }
 
     @Test
     public void testConstructorWithInvalidName() {
         assertThrows(InvalidTopicException.class,
-            () -> new ConfiguredInternalTopic("invalid topic name", 1, Optional.empty(), Collections.emptyMap()));
+            () -> new ConfiguredInternalTopic("invalid topic name", 1, Optional.empty(), Map.of()));
     }
 
     @Test
@@ -52,7 +51,7 @@ public class ConfiguredInternalTopicTest {
     @Test
     public void testConstructorWithZeroPartitions() {
         assertThrows(IllegalArgumentException.class,
-            () -> new ConfiguredInternalTopic("test-topic", 0, Optional.empty(), Collections.emptyMap()));
+            () -> new ConfiguredInternalTopic("test-topic", 0, Optional.empty(), Map.of()));
     }
 
     @Test

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredSubtopologyTest.java

@@ -20,7 +20,6 @@ import org.apache.kafka.common.message.StreamsGroupDescribeResponseData;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -38,9 +37,9 @@ public class ConfiguredSubtopologyTest {
         assertThrows(NullPointerException.class,
             () -> new ConfiguredSubtopology(
                 null,
-                Collections.emptyMap(),
+                Map.of(),
-                Collections.emptySet(),
+                Set.of(),
-                Collections.emptyMap()
+                Map.of()
             )
         );
     }
@@ -49,10 +48,10 @@ public class ConfiguredSubtopologyTest {
     public void testConstructorWithNullRepartitionSourceTopics() {
         assertThrows(NullPointerException.class,
             () -> new ConfiguredSubtopology(
-                Collections.emptySet(),
+                Set.of(),
                 null,
-                Collections.emptySet(),
+                Set.of(),
-                Collections.emptyMap()
+                Map.of()
             )
         );
     }
@@ -61,10 +60,10 @@ public class ConfiguredSubtopologyTest {
     public void testConstructorWithNullRepartitionSinkTopics() {
         assertThrows(NullPointerException.class,
             () -> new ConfiguredSubtopology(
-                Collections.emptySet(),
+                Set.of(),
-                Collections.emptyMap(),
+                Map.of(),
                 null,
-                Collections.emptyMap()
+                Map.of()
             )
         );
     }
@@ -73,9 +72,9 @@ public class ConfiguredSubtopologyTest {
     public void testConstructorWithNullStateChangelogTopics() {
         assertThrows(NullPointerException.class,
             () -> new ConfiguredSubtopology(
-                Collections.emptySet(),
+                Set.of(),
-                Collections.emptyMap(),
+                Map.of(),
-                Collections.emptySet(),
+                Set.of(),
                 null
             )
         );

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/ConfiguredTopologyTest.java

@@ -22,7 +22,6 @@ import org.apache.kafka.common.message.StreamsGroupDescribeResponseData;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -44,7 +43,7 @@ public class ConfiguredTopologyTest {
             () -> new ConfiguredTopology(
                 0,
                 null,
-                Collections.emptyMap(),
+                Map.of(),
                 Optional.empty()
             )
         );
@@ -68,7 +67,7 @@ public class ConfiguredTopologyTest {
             () -> new ConfiguredTopology(
                 0,
                 Optional.empty(),
-                Collections.emptyMap(),
+                Map.of(),
                 null
             )
         );
@@ -80,7 +79,7 @@ public class ConfiguredTopologyTest {
             () -> new ConfiguredTopology(
                 -1,
                 Optional.of(new TreeMap<>()),
-                Collections.emptyMap(),
+                Map.of(),
                 Optional.empty()
             )
         );
@@ -92,7 +91,7 @@ public class ConfiguredTopologyTest {
             () -> new ConfiguredTopology(
                 1,
                 Optional.empty(),
-                Collections.emptyMap(),
+                Map.of(),
                 Optional.empty()
             )
         );

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/CopartitionedTopicsEnforcerTest.java

@@ -21,7 +21,6 @@ import org.apache.kafka.common.utils.LogContext;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.Map;
 import java.util.OptionalInt;
 import java.util.Set;
@@ -49,7 +48,7 @@ public class CopartitionedTopicsEnforcerTest {
 
     @Test
     public void shouldThrowIllegalStateExceptionIfNoPartitionsFoundForCoPartitionedTopic() {
-        final Map<String, Integer> topicPartitionCounts = Collections.emptyMap();
+        final Map<String, Integer> topicPartitionCounts = Map.of();
         final CopartitionedTopicsEnforcer enforcer =
             new CopartitionedTopicsEnforcer(LOG_CONTEXT, topicPartitionProvider(topicPartitionCounts));
 

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/InternalTopicManagerTest.java

@@ -29,8 +29,8 @@ import org.apache.kafka.coordinator.group.streams.TopicMetadata;
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
@@ -94,7 +94,7 @@ class InternalTopicManagerTest {
                 .setReplicationFactor((short) -1)
                 .setConfigs(
                     new CreatableTopicConfigCollection(
-                        Collections.singletonList(new CreatableTopicConfig().setName(CONFIG_KEY).setValue(CONFIG_VALUE)).iterator())
+                        List.of(new CreatableTopicConfig().setName(CONFIG_KEY).setValue(CONFIG_VALUE)).iterator())
                 ),
             internalTopicsToBeCreated.get(STATE_CHANGELOG_TOPIC_1));
 
@@ -125,7 +125,7 @@ class InternalTopicManagerTest {
                         new ConfiguredInternalTopic(REPARTITION_TOPIC,
                             2,
                             Optional.of((short) 3),
-                            Collections.emptyMap()
+                            Map.of()
                         )
                     ),
                     Set.of(),
@@ -133,7 +133,7 @@ class InternalTopicManagerTest {
                         new ConfiguredInternalTopic(STATE_CHANGELOG_TOPIC_2,
                             2,
                             Optional.empty(),
-                            Collections.emptyMap()
+                            Map.of()
                         )))
             )
         );
@@ -143,12 +143,12 @@ class InternalTopicManagerTest {
         // Create a subtopology source -> repartition
         Subtopology subtopology1 = new Subtopology()
             .setSubtopologyId(SUBTOPOLOGY_1)
-            .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_1))
+            .setSourceTopics(List.of(SOURCE_TOPIC_1))
-            .setRepartitionSinkTopics(Collections.singletonList(REPARTITION_TOPIC))
+            .setRepartitionSinkTopics(List.of(REPARTITION_TOPIC))
-            .setStateChangelogTopics(Collections.singletonList(
+            .setStateChangelogTopics(List.of(
                 new StreamsGroupTopologyValue.TopicInfo()
                     .setName(STATE_CHANGELOG_TOPIC_1)
-                    .setTopicConfigs(Collections.singletonList(
+                    .setTopicConfigs(List.of(
                         new StreamsGroupTopologyValue.TopicConfig()
                             .setKey(CONFIG_KEY)
                             .setValue(CONFIG_VALUE)
@@ -157,20 +157,20 @@ class InternalTopicManagerTest {
         // Create a subtopology repartition/source2 -> sink (copartitioned)
         Subtopology subtopology2 = new Subtopology()
             .setSubtopologyId(SUBTOPOLOGY_2)
-            .setSourceTopics(Collections.singletonList(SOURCE_TOPIC_2))
+            .setSourceTopics(List.of(SOURCE_TOPIC_2))
-            .setRepartitionSourceTopics(Collections.singletonList(
+            .setRepartitionSourceTopics(List.of(
                 new StreamsGroupTopologyValue.TopicInfo()
                     .setName(REPARTITION_TOPIC)
                     .setReplicationFactor((short) 3)
             ))
-            .setStateChangelogTopics(Collections.singletonList(
+            .setStateChangelogTopics(List.of(
                 new StreamsGroupTopologyValue.TopicInfo()
                     .setName(STATE_CHANGELOG_TOPIC_2)
             ))
-            .setCopartitionGroups(Collections.singletonList(
+            .setCopartitionGroups(List.of(
                 new StreamsGroupTopologyValue.CopartitionGroup()
-                    .setSourceTopics(Collections.singletonList((short) 0))
+                    .setSourceTopics(List.of((short) 0))
-                    .setRepartitionSourceTopics(Collections.singletonList((short) 0))
+                    .setRepartitionSourceTopics(List.of((short) 0))
             ));
 
         return new StreamsTopology(3, Map.of(SUBTOPOLOGY_1, subtopology1, SUBTOPOLOGY_2, subtopology2));

group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/topics/RepartitionTopicsTest.java

@@ -23,7 +23,6 @@ import org.apache.kafka.coordinator.group.generated.StreamsGroupTopologyValue.To
 
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -198,7 +197,7 @@ public class RepartitionTopicsTest {
 
         final Map<String, Integer> setup = repartitionTopics.setup();
 
-        assertEquals(Collections.emptyMap(), setup);
+        assertEquals(Map.of(), setup);
     }
 
 }