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MINOR: remove unused FlattenedIterator (#20067)
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Remove FlattenedIterator. It’s no longer used anywhere after
https://github.com/apache/kafka/pull/20037.

Reviewers: TengYao Chi <kitingiao@gmail.com>, Lan Ding
 <isDing_L@163.com>, Chia-Ping Tsai <chia7712@gmail.com>
This commit is contained in:
Jhen-Yung Hsu 2025-06-30 20:02:08 +08:00 committed by GitHub
parent 53d654ab6e
commit 64aebb5621
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2 changed files with 0 additions and 161 deletions
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45
clients/src/main/java/org/apache/kafka/common/utils/FlattenedIterator.java
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@ -1,45 +0,0 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.common.utils;
import java.util.Iterator;
import java.util.function.Function;
/**
* Provides a flattened iterator over the inner elements of an outer iterator.
*/
public final class FlattenedIterator<O, I> extends AbstractIterator<I> {
private final Iterator<O> outerIterator;
private final Function<O, Iterator<I>> innerIteratorFunction;
private Iterator<I> innerIterator;
public FlattenedIterator(Iterator<O> outerIterator, Function<O, Iterator<I>> innerIteratorFunction) {
this.outerIterator = outerIterator;
this.innerIteratorFunction = innerIteratorFunction;
}
@Override
protected I makeNext() {
while (innerIterator == null || !innerIterator.hasNext()) {
if (outerIterator.hasNext())
innerIterator = innerIteratorFunction.apply(outerIterator.next());
else
return allDone();
}
return innerIterator.next();
}
}

116
clients/src/test/java/org/apache/kafka/common/utils/FlattenedIteratorTest.java
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@ -1,116 +0,0 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.common.utils;
import org.junit.jupiter.api.Test;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static org.junit.jupiter.api.Assertions.assertEquals;
public class FlattenedIteratorTest {
@Test
public void testNestedLists() {
List<List<String>> list = asList(
asList("foo", "a", "bc"),
Collections.singletonList("ddddd"),
asList("", "bar2", "baz45"));
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(list.stream().flatMap(Collection::stream).collect(Collectors.toList()), flattened);
// Ensure we can iterate multiple times
List<String> flattened2 = new ArrayList<>();
flattenedIterable.forEach(flattened2::add);
assertEquals(flattened, flattened2);
}
@Test
public void testEmptyList() {
List<List<String>> list = emptyList();
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(emptyList(), flattened);
}
@Test
public void testNestedSingleEmptyList() {
List<List<String>> list = Collections.singletonList(emptyList());
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(emptyList(), flattened);
}
@Test
public void testEmptyListFollowedByNonEmpty() {
List<List<String>> list = asList(
emptyList(),
asList("boo", "b", "de"));
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(list.stream().flatMap(Collection::stream).collect(Collectors.toList()), flattened);
}
@Test
public void testEmptyListInBetweenNonEmpty() {
List<List<String>> list = asList(
Collections.singletonList("aadwdwdw"),
emptyList(),
asList("ee", "aa", "dd"));
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(list.stream().flatMap(Collection::stream).collect(Collectors.toList()), flattened);
}
@Test
public void testEmptyListAtTheEnd() {
List<List<String>> list = asList(
asList("ee", "dd"),
Collections.singletonList("e"),
emptyList());
Iterable<String> flattenedIterable = () -> new FlattenedIterator<>(list.iterator(), List::iterator);
List<String> flattened = new ArrayList<>();
flattenedIterable.forEach(flattened::add);
assertEquals(list.stream().flatMap(Collection::stream).collect(Collectors.toList()), flattened);
}
}