IntelliJ inspection and checkstyle rule for "Collection.EMPTY_* field accesses replaceable with Collections.empty*()" (#9690)

* IntelliJ inspection and checkstyle rule for "Collection.EMPTY_* field accesses replaceable with Collections.empty*()"

* Reverted checkstyle rule

* Added tests to pass CI

* Codestyle

.idea/inspectionProfiles/Druid.xml

@@ -29,6 +29,7 @@
     <inspection_tool class="ClassNewInstance" enabled="true" level="WARNING" enabled_by_default="true" />
     <inspection_tool class="CollectionAddAllCanBeReplacedWithConstructor" enabled="true" level="ERROR" enabled_by_default="true" />
     <inspection_tool class="CollectionAddedToSelf" enabled="true" level="ERROR" enabled_by_default="true" />
+    <inspection_tool class="CollectionsFieldAccessReplaceableByMethodCall" enabled="true" level="ERROR" enabled_by_default="true" />
     <inspection_tool class="ComparableImplementedButEqualsNotOverridden" enabled="true" level="WARNING" enabled_by_default="true" />
     <inspection_tool class="ComparatorMethodParameterNotUsed" enabled="true" level="ERROR" enabled_by_default="true" />
     <inspection_tool class="ComparatorResultComparison" enabled="true" level="ERROR" enabled_by_default="true" />

extensions-contrib/ambari-metrics-emitter/src/test/java/org/apache/druid/emitter/ambari/metrics/AmbariMetricsEmitterConfigTest.java

@@ -56,7 +56,7 @@ public class AmbariMetricsEmitterConfigTest
         1000L,
         100,
         new SendAllTimelineEventConverter("prefix", "druid"),
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         500L,
         400L
     );

extensions-contrib/dropwizard-emitter/src/main/java/org/apache/druid/emitter/dropwizard/DropwizardEmitterModule.java

@@ -42,7 +42,7 @@ public class DropwizardEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/graphite-emitter/src/main/java/org/apache/druid/emitter/graphite/GraphiteEmitterModule.java

@@ -44,7 +44,7 @@ public class GraphiteEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/graphite-emitter/src/test/java/org/apache/druid/emitter/graphite/GraphiteEmitterConfigTest.java

@@ -53,8 +53,8 @@ public class GraphiteEmitterConfigTest
         1000L,
         100,
         new SendAllGraphiteEventConverter("prefix", true, true, false),
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         null,
         null
     );
@@ -92,4 +92,10 @@ public class GraphiteEmitterConfigTest
                                           .readValue(whiteListBasedConverterString);
     Assert.assertEquals(druidToGraphiteEventConverter, whiteListBasedConverter);
   }
+
+  @Test
+  public void testJacksonModules()
+  {
+    Assert.assertTrue(new GraphiteEmitterModule().getJacksonModules().isEmpty());
+  }
 }

extensions-contrib/influxdb-emitter/src/main/java/org/apache/druid/emitter/influxdb/InfluxdbEmitterModule.java

@@ -42,7 +42,7 @@ public class InfluxdbEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/influxdb-emitter/src/test/java/org/apache/druid/emitter/influxdb/InfluxdbEmitterTest.java

@@ -205,4 +205,10 @@ public class InfluxdbEmitterTest
     String actual = influxdbEmitter.transformForInfluxSystems(event);
     Assert.assertEquals(expected, actual);
   }
+
+  @Test
+  public void testJacksonModules()
+  {
+    Assert.assertTrue(new InfluxdbEmitterModule().getJacksonModules().isEmpty());
+  }
 }

extensions-contrib/kafka-emitter/src/main/java/org/apache/druid/emitter/kafka/KafkaEmitterModule.java

@@ -39,7 +39,7 @@ public class KafkaEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/kafka-emitter/src/test/java/org/apache/druid/emitter/kafka/KafkaEmitterConfigTest.java

@@ -68,4 +68,10 @@ public class KafkaEmitterConfigTest
       Assert.fail();
     }
   }
+
+  @Test
+  public void testJacksonModules()
+  {
+    Assert.assertTrue(new KafkaEmitterModule().getJacksonModules().isEmpty());
+  }
 }

extensions-contrib/opentsdb-emitter/src/main/java/org/apache/druid/emitter/opentsdb/OpentsdbEmitterModule.java

@@ -39,7 +39,7 @@ public class OpentsdbEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/opentsdb-emitter/src/test/java/org/apache/druid/emitter/opentsdb/OpentsdbEmitterConfigTest.java

@@ -76,4 +76,9 @@ public class OpentsdbEmitterConfigTest
     Assert.assertEquals(expectedOpentsdbEmitterConfig, opentsdbEmitterConfig);
   }
 
+  @Test
+  public void testJacksonModules()
+  {
+    Assert.assertTrue(new OpentsdbEmitterModule().getJacksonModules().isEmpty());
+  }
 }

extensions-contrib/statsd-emitter/src/main/java/org/apache/druid/emitter/statsd/StatsDEmitterModule.java

@@ -41,7 +41,7 @@ public class StatsDEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Override

extensions-contrib/statsd-emitter/src/test/java/org/apache/druid/emitter/statsd/StatsDEmitterTest.java

@@ -236,4 +236,10 @@ public class StatsDEmitterTest
     Assert.assertEquals(expectedEvent.getTitle(), actualEvent.getTitle());
     Assert.assertEquals(expectedEvent.getText(), actualEvent.getText());
   }
+
+  @Test
+  public void testJacksonModules()
+  {
+    Assert.assertTrue(new StatsDEmitterModule().getJacksonModules().isEmpty());
+  }
 }

extensions-core/kafka-indexing-service/src/test/java/org/apache/druid/indexing/kafka/supervisor/KafkaSupervisorTest.java

@@ -780,7 +780,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(Status.NOT_STARTED))
@@ -928,7 +928,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(Status.NOT_STARTED))
@@ -1032,7 +1032,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance();
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id1")).andReturn(Optional.of(TaskStatus.running("id1"))).anyTimes();
     EasyMock.expect(taskStorage.getTask("id1")).andReturn(Optional.of(id1)).anyTimes();
@@ -1121,7 +1121,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(Status.NOT_STARTED))
@@ -1224,7 +1224,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KafkaDataSourceMetadata(
@@ -1722,7 +1722,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KafkaDataSourceMetadata(
@@ -1808,7 +1808,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KafkaDataSourceMetadata(
@@ -2032,7 +2032,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
   {
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2057,7 +2057,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     supervisor = getTestableSupervisor(1, 1, true, "PT1H", null, null);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2113,7 +2113,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     supervisor = getTestableSupervisor(1, 1, true, "PT1H", null, null);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2146,7 +2146,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     supervisor = getTestableSupervisor(1, 1, true, true, "PT1H", null, null);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
 
@@ -2749,7 +2749,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
   {
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2960,7 +2960,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id1")).andReturn(Optional.of(TaskStatus.running("id1"))).anyTimes();
     EasyMock.expect(taskStorage.getTask("id1")).andReturn(Optional.of(task)).anyTimes();
@@ -3029,7 +3029,7 @@ public class KafkaSupervisorTest extends EasyMockSupport
     List<Task> existingTasks = ImmutableList.of(task);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id1")).andReturn(Optional.of(TaskStatus.running("id1"))).anyTimes();
     EasyMock.expect(taskStorage.getTask("id1")).andReturn(Optional.of(task)).anyTimes();

extensions-core/kinesis-indexing-service/src/test/java/org/apache/druid/indexing/kinesis/supervisor/KinesisSupervisorTest.java

@@ -721,7 +721,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -815,7 +815,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id1")).andReturn(Optional.of(TaskStatus.running("id1"))).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id2")).andReturn(Optional.of(TaskStatus.running("id2"))).anyTimes();
@@ -886,7 +886,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -1134,7 +1134,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -1260,7 +1260,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     final Capture<Task> firstTasks = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KinesisDataSourceMetadata(null)
@@ -1882,7 +1882,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KinesisDataSourceMetadata(
@@ -1964,7 +1964,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KinesisDataSourceMetadata(
@@ -2072,7 +2072,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(indexerMetadataStorageCoordinator.retrieveDataSourceMetadata(DATASOURCE)).andReturn(
         new KinesisDataSourceMetadata(
@@ -2380,7 +2380,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2410,7 +2410,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     supervisor = getTestableSupervisor(1, 1, true, "PT1H", null, null);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -2538,7 +2538,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
 
     EasyMock.reset(indexerMetadataStorageCoordinator);
@@ -3409,7 +3409,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
             .anyTimes();
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     taskRunner.registerListener(EasyMock.anyObject(TaskRunnerListener.class), EasyMock.anyObject(Executor.class));
     replayAll();
@@ -3536,7 +3536,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id2")).andReturn(Optional.of(TaskStatus.running("id2"))).anyTimes();
     EasyMock.expect(taskStorage.getTask("id2")).andReturn(Optional.of(task)).anyTimes();
@@ -3633,7 +3633,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(existingTasks).anyTimes();
     EasyMock.expect(taskStorage.getStatus("id1")).andReturn(Optional.of(TaskStatus.running("id1"))).anyTimes();
     EasyMock.expect(taskStorage.getTask("id1")).andReturn(Optional.of(task)).anyTimes();
@@ -3850,7 +3850,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -3959,7 +3959,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -4134,7 +4134,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -4296,7 +4296,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
     Capture<Task> captured = Capture.newInstance(CaptureType.ALL);
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -4416,7 +4416,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))
@@ -4570,7 +4570,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
 
     EasyMock.expect(taskMaster.getTaskQueue()).andReturn(Optional.of(taskQueue)).anyTimes();
     EasyMock.expect(taskMaster.getTaskRunner()).andReturn(Optional.of(taskRunner)).anyTimes();
-    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.EMPTY_LIST).anyTimes();
+    EasyMock.expect(taskRunner.getRunningTasks()).andReturn(Collections.emptyList()).anyTimes();
     EasyMock.expect(taskStorage.getActiveTasksByDatasource(DATASOURCE)).andReturn(ImmutableList.of()).anyTimes();
     EasyMock.expect(taskClient.getStatusAsync(EasyMock.anyString()))
             .andReturn(Futures.immediateFuture(SeekableStreamIndexTaskRunner.Status.NOT_STARTED))

extensions-core/lookups-cached-single/src/test/java/org/apache/druid/server/lookup/PollingLookupTest.java

@@ -177,7 +177,7 @@ public class PollingLookupTest extends InitializedNullHandlingTest
     );
     Assert.assertEquals(
         "reverse lookup of none existing value should be empty list",
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         pollingLookup.unapply("does't exist")
     );
   }

extensions-core/lookups-cached-single/src/test/java/org/apache/druid/server/lookup/cache/loading/LoadingCacheTest.java

@@ -141,7 +141,7 @@ public class LoadingCacheTest
         return "value2";
       }
     });
-    Assert.assertEquals(loadingCache.getAllPresent(IMMUTABLE_MAP.keySet()), Collections.EMPTY_MAP);
+    Assert.assertEquals(loadingCache.getAllPresent(IMMUTABLE_MAP.keySet()), Collections.emptyMap());
   }
 
   @Test

extensions-core/lookups-cached-single/src/test/java/org/apache/druid/server/lookup/jdbc/JdbcDataFetcherTest.java

@@ -147,7 +147,7 @@ public class JdbcDataFetcherTest extends InitializedNullHandlingTest
       );
       Assert.assertEquals(
           "reverse lookup of none existing value should be empty list",
-          Collections.EMPTY_LIST,
+          Collections.emptyList(),
           jdbcDataFetcher.reverseFetchKeys("does't exist")
       );
     }

indexing-hadoop/src/test/java/org/apache/druid/indexer/InputRowSerdeTest.java

@@ -147,7 +147,7 @@ public class InputRowSerdeTest
 
     Assert.assertEquals(timestamp, out.getTimestampFromEpoch());
     Assert.assertEquals(dims, out.getDimensions());
-    Assert.assertEquals(Collections.EMPTY_LIST, out.getDimension("dim_non_existing"));
+    Assert.assertEquals(Collections.emptyList(), out.getDimension("dim_non_existing"));
     Assert.assertEquals(ImmutableList.of("d1v"), out.getDimension("d1"));
     Assert.assertEquals(ImmutableList.of("d2v1", "d2v2"), out.getDimension("d2"));
     Assert.assertEquals(200L, out.getRaw("d3"));

indexing-service/src/main/java/org/apache/druid/indexing/overlord/setup/WorkerCategorySpec.java

@@ -38,7 +38,7 @@ public class WorkerCategorySpec
       @JsonProperty("strong") boolean strong
   )
   {
-    this.categoryMap = categoryMap == null ? Collections.EMPTY_MAP : categoryMap;
+    this.categoryMap = categoryMap == null ? Collections.emptyMap() : categoryMap;
     this.strong = strong;
   }
 
@@ -96,7 +96,7 @@ public class WorkerCategorySpec
     )
     {
       this.defaultCategory = defaultCategory;
-      this.categoryAffinity = categoryAffinity == null ? Collections.EMPTY_MAP : categoryAffinity;
+      this.categoryAffinity = categoryAffinity == null ? Collections.emptyMap() : categoryAffinity;
     }
 
     @JsonProperty

integration-tests/src/main/java/org/apache/druid/testing/guice/ITTLSCertificateCheckerModule.java

@@ -46,7 +46,7 @@ public class ITTLSCertificateCheckerModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 }
 

processing/src/main/java/org/apache/druid/query/lookup/LookupsState.java

@@ -42,9 +42,9 @@ public class LookupsState<T>
       @JsonProperty("toDrop") Set<String> toDrop
   )
   {
-    this.current = current == null ? Collections.EMPTY_MAP : current;
+    this.current = current == null ? Collections.emptyMap() : current;
-    this.toLoad = toLoad == null ? Collections.EMPTY_MAP : toLoad;
+    this.toLoad = toLoad == null ? Collections.emptyMap() : toLoad;
-    this.toDrop = toDrop == null ? Collections.EMPTY_SET : toDrop;
+    this.toDrop = toDrop == null ? Collections.emptySet() : toDrop;
   }
 
   @JsonProperty

processing/src/test/java/org/apache/druid/query/aggregation/StringColumnAggregationTest.java

@@ -96,7 +96,7 @@ public class StringColumnAggregationTest
     }
 
     aggregationTestHelper = AggregationTestHelper.createGroupByQueryAggregationTestHelper(
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         new GroupByQueryConfig(),
         tempFolder
     );
@@ -231,7 +231,7 @@ public class StringColumnAggregationTest
                                   )
                                   .build();
 
-    Sequence seq = AggregationTestHelper.createTimeseriesQueryAggregationTestHelper(Collections.EMPTY_LIST, tempFolder)
+    Sequence seq = AggregationTestHelper.createTimeseriesQueryAggregationTestHelper(Collections.emptyList(), tempFolder)
                                         .runQueryOnSegmentsObjs(segments, query);
     TimeseriesResultValue result = ((Result<TimeseriesResultValue>) Iterables.getOnlyElement(seq.toList())).getValue();
 

processing/src/test/java/org/apache/druid/query/aggregation/mean/DoubleMeanAggregationTest.java

@@ -72,13 +72,13 @@ public class DoubleMeanAggregationTest
   {
 
     groupByQueryTestHelper = AggregationTestHelper.createGroupByQueryAggregationTestHelper(
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         new GroupByQueryConfig(),
         tempFolder
     );
 
     timeseriesQueryTestHelper = AggregationTestHelper.createTimeseriesQueryAggregationTestHelper(
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         tempFolder
     );
 

processing/src/test/java/org/apache/druid/query/extraction/MapLookupExtractorTest.java

@@ -64,7 +64,7 @@ public class MapLookupExtractorTest
       );
     }
     Assert.assertEquals(Sets.newHashSet(""), Sets.newHashSet(fn.unapply("empty_string")));
-    Assert.assertEquals("not existing value returns empty list", Collections.EMPTY_LIST, fn.unapply("not There"));
+    Assert.assertEquals("not existing value returns empty list", Collections.emptyList(), fn.unapply("not There"));
   }
 
   @Test

processing/src/test/java/org/apache/druid/query/groupby/GroupByQueryRunnerTest.java

@@ -9879,7 +9879,7 @@ public class GroupByQueryRunnerTest extends InitializedNullHandlingTest
         .setInterval(QueryRunnerTestHelper.FULL_ON_INTERVAL_SPEC)
         .setLimitSpec(
             new DefaultLimitSpec(
-                Collections.EMPTY_LIST,
+                Collections.emptyList(),
                 6
             )
         ).setAggregatorSpecs(QueryRunnerTestHelper.ROWS_COUNT)

processing/src/test/java/org/apache/druid/query/groupby/orderby/TopNSequenceTest.java

@@ -42,7 +42,7 @@ public class TopNSequenceTest
   private static final Ordering<String> ASC = Ordering.natural();
   private static final Ordering<String> DESC = Ordering.natural().reverse();
 
-  private static final List<String> EMPTY = Collections.EMPTY_LIST;
+  private static final List<String> EMPTY = Collections.emptyList();
   private static final List<String> SINGLE = Collections.singletonList("a");
   private static final List<String> RAW_ASC = Lists.newArrayList(Splitter.fixedLength(1).split("abcdefghijk"));
   private static final List<String> RAW_DESC = Lists.newArrayList(Splitter.fixedLength(1).split("kjihgfedcba"));

processing/src/test/java/org/apache/druid/segment/virtual/DummyStringVirtualColumnTest.java

@@ -79,12 +79,12 @@ public class DummyStringVirtualColumnTest extends InitializedNullHandlingTest
     mixedSegments = Lists.newArrayList(incrementalIndexSegment, queryableIndexSegment);
 
     topNTestHelper = AggregationTestHelper.createTopNQueryAggregationTestHelper(
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         null
     );
 
     groupByTestHelper = AggregationTestHelper.createGroupByQueryAggregationTestHelper(
-        Collections.EMPTY_LIST,
+        Collections.emptyList(),
         new GroupByQueryConfig(),
         null
     );

server/src/main/java/org/apache/druid/server/emitter/ComposingEmitterModule.java

@@ -53,7 +53,7 @@ public class ComposingEmitterModule implements DruidModule
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   @Provides

server/src/main/java/org/apache/druid/server/initialization/AuthenticatorMapperModule.java

@@ -62,11 +62,10 @@ public class AuthenticatorMapperModule implements DruidModule
     LifecycleModule.register(binder, AuthenticatorMapper.class);
   }
 
-  @SuppressWarnings("unchecked")
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   private static class AuthenticatorMapperProvider implements Provider<AuthenticatorMapper>

server/src/main/java/org/apache/druid/server/initialization/AuthorizerMapperModule.java

@@ -62,11 +62,10 @@ public class AuthorizerMapperModule implements DruidModule
     LifecycleModule.register(binder, AuthorizerMapper.class);
   }
 
-  @SuppressWarnings("unchecked")
   @Override
   public List<? extends Module> getJacksonModules()
   {
-    return Collections.EMPTY_LIST;
+    return Collections.emptyList();
   }
 
   private static class AuthorizerMapperProvider implements Provider<AuthorizerMapper>

server/src/test/java/org/apache/druid/query/lookup/LookupSnapshotTakerTest.java

@@ -125,7 +125,7 @@ public class LookupSnapshotTakerTest
   {
     File snapshotFile = lookupSnapshotTaker.getPersistFile(TIER1);
     Assert.assertTrue(snapshotFile.createNewFile());
-    Assert.assertEquals(Collections.EMPTY_LIST, lookupSnapshotTaker.pullExistingSnapshot(TIER1));
+    Assert.assertEquals(Collections.emptyList(), lookupSnapshotTaker.pullExistingSnapshot(TIER1));
   }
 
   @Test(expected = ISE.class)
@@ -144,6 +144,6 @@ public class LookupSnapshotTakerTest
     File directory = temporaryFolder.newFolder();
     LookupSnapshotTaker lookupSnapshotTaker = new LookupSnapshotTaker(mapper, directory.getAbsolutePath());
     List<LookupBean> actualList = lookupSnapshotTaker.pullExistingSnapshot(TIER1);
-    Assert.assertEquals(Collections.EMPTY_LIST, actualList);
+    Assert.assertEquals(Collections.emptyList(), actualList);
   }
 }

server/src/test/java/org/apache/druid/server/lookup/cache/LookupCoordinatorManagerTest.java

@@ -108,7 +108,7 @@ public class LookupCoordinatorManagerTest
   private static final LookupsState<LookupExtractorFactoryMapContainer> LOOKUPS_STATE = new LookupsState<>(
       SINGLE_LOOKUP_MAP_V0,
       SINGLE_LOOKUP_MAP_V1,
-      Collections.EMPTY_SET
+      Collections.emptySet()
   );
 
   private static final AtomicLong EVENT_EMITS = new AtomicLong(0L);
@@ -1352,7 +1352,7 @@ public class LookupCoordinatorManagerTest
                         EasyMock.<TypeReference>anyObject(),
                         EasyMock.<AtomicReference>isNull()
                     )).andReturn(
-        new AtomicReference<>(Collections.EMPTY_MAP)).anyTimes();
+        new AtomicReference<>(Collections.emptyMap())).anyTimes();
 
     EasyMock.replay(configManager);
 

server/src/test/java/org/apache/druid/server/shard/NumberedShardSpecTest.java

@@ -128,29 +128,29 @@ public class NumberedShardSpecTest
     //incomplete partition sets
     testVersionedIntervalTimelineBehaviorForNumberedShardSpec(
         ImmutableList.of(chunk0),
-        Collections.EMPTY_SET
+        Collections.emptySet()
     );
 
     testVersionedIntervalTimelineBehaviorForNumberedShardSpec(
         ImmutableList.of(chunk1),
-        Collections.EMPTY_SET
+        Collections.emptySet()
     );
 
     testVersionedIntervalTimelineBehaviorForNumberedShardSpec(
         ImmutableList.of(chunk4),
-        Collections.EMPTY_SET
+        Collections.emptySet()
     );
 
 
     testVersionedIntervalTimelineBehaviorForNumberedShardSpec(
         ImmutableList.of(chunk0, chunk4),
-        Collections.EMPTY_SET
+        Collections.emptySet()
     );
 
 
     testVersionedIntervalTimelineBehaviorForNumberedShardSpec(
         ImmutableList.of(chunk1, chunk4),
-        Collections.EMPTY_SET
+        Collections.emptySet()
     );
 
     //complete partition sets