KAFKA-16564 Apply `Xlint` to java code in core module (#16965)

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

build.gradle

@@ -113,11 +113,22 @@ ext {
 
   commitId = determineCommitId()
 
-  addParametersForTests = { name, options ->
+  configureJavaCompiler = { name, options ->
     // -parameters generates arguments with parameter names in TestInfo#getDisplayName.
     // ref: https://github.com/junit-team/junit5/blob/4c0dddad1b96d4a20e92a2cd583954643ac56ac0/junit-jupiter-params/src/main/java/org/junit/jupiter/params/ParameterizedTest.java#L161-L164
-    if (name == "compileTestJava" || name == "compileTestScala")
+    if (name == "compileTestJava" || name == "compileTestScala") {
       options.compilerArgs << "-parameters"
+    } else if (name == "compileJava" || name == "compileScala") {
+      options.compilerArgs << "-Xlint:all"
+      if (!project.path.startsWith(":connect") && !project.path.startsWith(":storage"))
+        options.compilerArgs << "-Xlint:-rawtypes"
+      options.compilerArgs << "-encoding" << "UTF-8"
+      options.compilerArgs << "-Xlint:-rawtypes"
+      options.compilerArgs << "-Xlint:-serial"
+      options.compilerArgs << "-Xlint:-try"
+      options.compilerArgs << "-Werror"
+      options.compilerArgs += ["--release", String.valueOf(minJavaVersion)]
+    }
   }
 
   runtimeTestLibs = [
@@ -308,16 +319,7 @@ subprojects {
   }
 
   tasks.withType(JavaCompile) {
-    options.encoding = 'UTF-8'
-    options.compilerArgs << "-Xlint:all"
-    // temporary exclusions until all the warnings are fixed
-    if (!project.path.startsWith(":connect") && !project.path.startsWith(":storage"))
-      options.compilerArgs << "-Xlint:-rawtypes"
-    options.compilerArgs << "-Xlint:-serial"
-    options.compilerArgs << "-Xlint:-try"
-    options.compilerArgs << "-Werror"
-    options.release = minJavaVersion
-    addParametersForTests(name, options)
+    configureJavaCompiler(name, options)
   }
 
   if (shouldPublish) {
@@ -769,9 +771,8 @@ subprojects {
     scalaCompileOptions.additionalParameters += ["-Xfatal-warnings"]
 
     scalaCompileOptions.additionalParameters += ["-release", String.valueOf(minJavaVersion)]
-    options.compilerArgs += ["--release", String.valueOf(minJavaVersion)]
 
-    addParametersForTests(name, options)
+    configureJavaCompiler(name, options)
 
     configure(scalaCompileOptions.forkOptions) {
       memoryMaximumSize = defaultMaxHeapSize

connect/runtime/src/test/java/org/apache/kafka/connect/runtime/isolation/SynchronizationTest.java

@@ -456,6 +456,7 @@ public class SynchronizationTest {
         }
     }
 
+    @SuppressWarnings("removal")
     private static ThreadFactory threadFactoryWithNamedThreads(String threadPrefix) {
         AtomicInteger threadNumber = new AtomicInteger(1);
         return r -> {

core/src/main/java/kafka/log/remote/RemoteLogManager.java

@@ -221,6 +221,7 @@ public class RemoteLogManager implements Closeable {
      * @param brokerTopicStats BrokerTopicStats instance to update the respective metrics.
      * @param metrics  Metrics instance
      */
+    @SuppressWarnings({"this-escape"})
     public RemoteLogManager(RemoteLogManagerConfig rlmConfig,
                             int brokerId,
                             String logDir,
@@ -331,6 +332,7 @@ public class RemoteLogManager implements Closeable {
           rlmConfig.remoteLogManagerFetchQuotaWindowSizeSeconds());
     }
 
+    @SuppressWarnings("unchecked")
     private <T> T createDelegate(ClassLoader classLoader, String className) {
         try {
             return (T) classLoader.loadClass(className)

core/src/test/java/kafka/admin/ConfigCommandTest.java

@@ -1312,6 +1312,7 @@ public class ConfigCommandTest {
                 return describeResult;
             }
 
+            @SuppressWarnings("deprecation")
             @Override
             public synchronized AlterConfigsResult alterConfigs(Map<ConfigResource, Config> configs, AlterConfigsOptions options) {
                 assertEquals(1, configs.size());