Clean up some older collections idioms in ILM (#118508) (#118582)

Author: joegallo

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/AllocateAction.java

@@ -20,8 +20,6 @@
 import org.elasticsearch.xpack.core.ilm.Step.StepKey;
 
 import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -73,17 +71,17 @@ public AllocateAction(
         Map<String, String> require
     ) {
         if (include == null) {
-            this.include = Collections.emptyMap();
+            this.include = Map.of();
         } else {
             this.include = include;
         }
         if (exclude == null) {
-            this.exclude = Collections.emptyMap();
+            this.exclude = Map.of();
         } else {
             this.exclude = exclude;
         }
         if (require == null) {
-            this.require = Collections.emptyMap();
+            this.require = Map.of();
         } else {
             this.require = require;
         }
@@ -201,7 +199,7 @@ public List<Step> toSteps(Client client, String phase, StepKey nextStepKey) {
         }
         UpdateSettingsStep allocateStep = new UpdateSettingsStep(allocateKey, allocationRoutedKey, client, newSettings.build());
         AllocationRoutedStep routedCheckStep = new AllocationRoutedStep(allocationRoutedKey, nextStepKey);
-        return Arrays.asList(allocateStep, routedCheckStep);
+        return List.of(allocateStep, routedCheckStep);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/AllocationRoutedStep.java

@@ -22,7 +22,7 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.Index;
 
-import java.util.Collections;
+import java.util.List;
 
 import static org.elasticsearch.xpack.core.ilm.step.info.AllocationInfo.allShardsActiveAllocationInfo;
 import static org.elasticsearch.xpack.core.ilm.step.info.AllocationInfo.waitingForActiveShardsAllocationInfo;
@@ -62,7 +62,7 @@ public Result isConditionMet(Index index, ClusterState clusterState) {
         }
 
         AllocationDeciders allocationDeciders = new AllocationDeciders(
-            Collections.singletonList(
+            List.of(
                 new FilterAllocationDecider(
                     clusterState.getMetadata().settings(),
                     new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS)

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/DeleteAction.java

@@ -17,7 +17,6 @@
 
 import java.io.IOException;
 import java.time.Instant;
-import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
 
@@ -99,7 +98,7 @@ public List<Step> toSteps(Client client, String phase, Step.StepKey nextStepKey)
             );
             CleanupSnapshotStep cleanupSnapshotStep = new CleanupSnapshotStep(cleanSnapshotKey, deleteStepKey, client);
             DeleteStep deleteStep = new DeleteStep(deleteStepKey, nextStepKey, client);
-            return Arrays.asList(waitForNoFollowersStep, waitUntilTimeSeriesEndTimeStep, cleanupSnapshotStep, deleteStep);
+            return List.of(waitForNoFollowersStep, waitUntilTimeSeriesEndTimeStep, cleanupSnapshotStep, deleteStep);
         } else {
             WaitForNoFollowersStep waitForNoFollowersStep = new WaitForNoFollowersStep(
                 waitForNoFollowerStepKey,
@@ -113,7 +112,7 @@ public List<Step> toSteps(Client client, String phase, Step.StepKey nextStepKey)
                 client
             );
             DeleteStep deleteStep = new DeleteStep(deleteStepKey, nextStepKey, client);
-            return Arrays.asList(waitForNoFollowersStep, waitUntilTimeSeriesEndTimeStep, deleteStep);
+            return List.of(waitForNoFollowersStep, waitUntilTimeSeriesEndTimeStep, deleteStep);
         }
     }
 

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ForceMergeStep.java

@@ -20,7 +20,6 @@
 
 import java.util.Arrays;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 /**
  * Invokes a force merge on a single index.
@@ -67,10 +66,7 @@ public void performAction(
                     policyName,
                     failures == null
                         ? "n/a"
-                        : Strings.collectionToDelimitedString(
-                            Arrays.stream(failures).map(Strings::toString).collect(Collectors.toList()),
-                            ","
-                        ),
+                        : Strings.collectionToDelimitedString(Arrays.stream(failures).map(Strings::toString).toList(), ","),
                     NAME
                 );
                 logger.warn(errorMessage);

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/FreezeAction.java

@@ -18,7 +18,6 @@
 import org.elasticsearch.xpack.core.ilm.Step.StepKey;
 
 import java.io.IOException;
-import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -98,7 +97,7 @@ public List<Step> toSteps(Client client, String phase, StepKey nextStepKey) {
         );
         CheckNotDataStreamWriteIndexStep checkNoWriteIndexStep = new CheckNotDataStreamWriteIndexStep(checkNotWriteIndex, freezeStepKey);
         FreezeStep freezeStep = new FreezeStep(freezeStepKey, nextStepKey, client);
-        return Arrays.asList(conditionalSkipFreezeStep, checkNoWriteIndexStep, freezeStep);
+        return List.of(conditionalSkipFreezeStep, checkNoWriteIndexStep, freezeStep);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/LifecyclePolicyUtils.java

@@ -26,7 +26,6 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 
 /**
  * A utility class used for index lifecycle policies
@@ -121,7 +120,7 @@ public static ItemUsage calculateUsage(
             .stream()
             .filter(indexMetadata -> policyName.equals(indexMetadata.getLifecyclePolicyName()))
             .map(indexMetadata -> indexMetadata.getIndex().getName())
-            .collect(Collectors.toList());
+            .toList();
 
         final List<String> allDataStreams = indexNameExpressionResolver.dataStreamNames(
             state,
@@ -136,12 +135,12 @@ public static ItemUsage calculateUsage(
             } else {
                 return false;
             }
-        }).collect(Collectors.toList());
+        }).toList();
 
         final List<String> composableTemplates = state.metadata().templatesV2().keySet().stream().filter(templateName -> {
             Settings settings = MetadataIndexTemplateService.resolveSettings(state.metadata(), templateName);
             return policyName.equals(LifecycleSettings.LIFECYCLE_NAME_SETTING.get(settings));
-        }).collect(Collectors.toList());
+        }).toList();
 
         return new ItemUsage(indices, dataStreams, composableTemplates);
     }

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ReadOnlyAction.java

@@ -17,7 +17,6 @@
 
 import java.io.IOException;
 import java.time.Instant;
-import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -72,7 +71,7 @@ public List<Step> toSteps(Client client, String phase, StepKey nextStepKey) {
             client
         );
         ReadOnlyStep readOnlyStep = new ReadOnlyStep(readOnlyKey, nextStepKey, client);
-        return Arrays.asList(checkNotWriteIndexStep, waitUntilTimeSeriesEndTimeStep, readOnlyStep);
+        return List.of(checkNotWriteIndexStep, waitUntilTimeSeriesEndTimeStep, readOnlyStep);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/RolloverAction.java

@@ -22,7 +22,6 @@
 import org.elasticsearch.xpack.core.ilm.Step.StepKey;
 
 import java.io.IOException;
-import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
 
@@ -172,7 +171,7 @@ public List<Step> toSteps(Client client, String phase, Step.StepKey nextStepKey)
             client,
             INDEXING_COMPLETE
         );
-        return Arrays.asList(waitForRolloverReadyStep, rolloverStep, waitForActiveShardsStep, updateDateStep, setIndexingCompleteStep);
+        return List.of(waitForRolloverReadyStep, rolloverStep, waitForActiveShardsStep, updateDateStep, setIndexingCompleteStep);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/SegmentCountStep.java

@@ -67,10 +67,7 @@ public void evaluateCondition(Metadata metadata, Index index, Listener listener,
                     response.getFailedShards(),
                     failures == null
                         ? "n/a"
-                        : Strings.collectionToDelimitedString(
-                            Arrays.stream(failures).map(Strings::toString).collect(Collectors.toList()),
-                            ","
-                        )
+                        : Strings.collectionToDelimitedString(Arrays.stream(failures).map(Strings::toString).toList(), ",")
                 );
                 listener.onResponse(true, new Info(-1));
             } else {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/SetPriorityAction.java

@@ -21,7 +21,6 @@
 import org.elasticsearch.xpack.core.ilm.Step.StepKey;
 
 import java.io.IOException;
-import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -101,7 +100,7 @@ public List<Step> toSteps(Client client, String phase, StepKey nextStepKey) {
         Settings indexPriority = recoveryPriority == null
             ? NULL_PRIORITY_SETTINGS
             : Settings.builder().put(IndexMetadata.INDEX_PRIORITY_SETTING.getKey(), recoveryPriority).build();
-        return Collections.singletonList(new UpdateSettingsStep(key, nextStepKey, client, indexPriority));
+        return List.of(new UpdateSettingsStep(key, nextStepKey, client, indexPriority));
     }
 
     @Override