SOLR-18164: Remove use of .singleton

gradle/validation/forbidden-apis/defaults.all.txt

@@ -63,6 +63,15 @@ java.util.Collections#emptySet()
 @defaultMessage Use Map.of()
 java.util.Collections#emptyMap()
 
+@defaultMessage Use Set.of()
+java.util.Collections#singleton(**)
+
+@defaultMessage Use List.of()
+java.util.Collections#singletonList(**)
+
+@defaultMessage Use Map.of()
+java.util.Collections#singletonMap(**)
+
 java.util.Locale#forLanguageTag(java.lang.String) @ use new Locale.Builder().setLanguageTag(...).build() which has error handling
 java.util.Locale#toString() @ use Locale#toLanguageTag() for a standardized BCP47 locale name
 

solr/benchmark/src/java/org/apache/solr/bench/generators/Maps.java

@@ -16,7 +16,6 @@
  */
 package org.apache.solr.bench.generators;
 
-import java.util.Collections;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Collector;
@@ -105,6 +104,6 @@ private static <K, V> AsString<Map<K, V>> mapDescriber(
    * @return the map . entry
    */
   static <K, V> Map.Entry<K, V> mapEntry(K k, V v) {
-    return Collections.singletonMap(k, v).entrySet().iterator().next();
+    return Map.of(k, v).entrySet().iterator().next();
   }
 }

solr/benchmark/src/test/org/apache/solr/bench/SolrBenchStateTest.java

@@ -26,7 +26,7 @@
 import static org.apache.solr.bench.generators.SourceDSL.strings;
 
 import com.carrotsearch.randomizedtesting.annotations.ThreadLeakLingering;
-import java.util.Collections;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.client.solrj.request.QueryRequest;
@@ -61,7 +61,7 @@ public void test() throws Exception {
             true,
             1,
             new int[] {1},
-            Collections.singletonList("label"),
+            List.of("label"),
             0,
             0,
             new IterationParams(IterationType.WARMUP, 1, TimeValue.milliseconds(10), 1),
@@ -71,7 +71,7 @@ public void test() throws Exception {
             TimeUnit.SECONDS,
             1,
             "jvm",
-            Collections.singletonList("jvmArg"),
+            List.of("jvmArg"),
             "jdkVersion",
             "vmName",
             "vmVersion",

solr/core/src/java/org/apache/solr/api/AnnotatedApi.java

@@ -29,7 +29,6 @@
 import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -130,15 +129,15 @@ public static List<Api> getApis(Class<?> theClass, Object obj, boolean allowEmpt
         throw new RuntimeException("No method with @Command in class: " + klas.getName());
       }
       SpecProvider specProvider = readSpec(endPoint, methods);
-      return Collections.singletonList(new AnnotatedApi(specProvider, endPoint, commands, null));
+      return List.of(new AnnotatedApi(specProvider, endPoint, commands, null));
     } else {
       List<Api> apis = new ArrayList<>();
       for (Method m : klas.getMethods()) {
         EndPoint endPoint = m.getAnnotation(EndPoint.class);
         if (endPoint == null) continue;
         Cmd cmd = new Cmd("", obj, m);
-        SpecProvider specProvider = readSpec(endPoint, Collections.singletonList(m));
-        apis.add(new AnnotatedApi(specProvider, endPoint, Collections.singletonMap("", cmd), null));
+        SpecProvider specProvider = readSpec(endPoint, List.of(m));
+        apis.add(new AnnotatedApi(specProvider, endPoint, Map.of("", cmd), null));
       }
       if (!allowEmpty && apis.isEmpty()) {
         throw new RuntimeException("Invalid Class : " + klas.getName() + " No @EndPoints");
@@ -170,9 +169,7 @@ private static SpecProvider readSpec(EndPoint endPoint, List<Method> m) {
         methods.add(method.name());
       }
       map.put("methods", methods);
-      map.put(
-          "url",
-          new ValidatingJsonMap(Collections.singletonMap("paths", Arrays.asList(endPoint.path()))));
+      map.put("url", new ValidatingJsonMap(Map.of("paths", Arrays.asList(endPoint.path()))));
       Map<String, Object> cmds = new HashMap<>();
 
       for (Method method : m) {
@@ -359,7 +356,7 @@ private void checkForErrorInPayload(CommandOperation cmd) {
         throw new SolrErrorWrappingException(
             SolrException.ErrorCode.BAD_REQUEST,
             "Error executing command",
-            CommandOperation.captureErrors(Collections.singletonList(cmd)));
+            CommandOperation.captureErrors(List.of(cmd)));
       }
     }
   }

solr/core/src/java/org/apache/solr/api/ApiBag.java

@@ -28,7 +28,6 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -276,9 +275,9 @@ public void call(SolrQueryRequest req, SolrQueryResponse rsp) {
         if (commands != null) {
           ValidatingJsonMap m = commands.getMap(cmd, null);
           if (m == null) {
-            specCopy.put("commands", Collections.singletonMap(cmd, "Command not found!"));
+            specCopy.put("commands", Map.of(cmd, "Command not found!"));
           } else {
-            specCopy.put("commands", Collections.singletonMap(cmd, m));
+            specCopy.put("commands", Map.of(cmd, m));
           }
         }
         result = specCopy;
@@ -386,7 +385,7 @@ public static List<Api> wrapRequestHandlers(final SolrRequestHandler rh, String.
         final ValidatingJsonMap spec = new ValidatingJsonMap();
         spec.put("methods", List.of("GET", "POST"));
         final ValidatingJsonMap urlMap = new ValidatingJsonMap();
-        urlMap.put("paths", Collections.singletonList("$" + HANDLER_NAME));
+        urlMap.put("paths", List.of("$" + HANDLER_NAME));
         spec.put("url", urlMap);
         return spec;
       };
@@ -398,7 +397,7 @@ public PathTrie<Api> getRegistry(String method) {
   public void registerLazy(PluginBag.PluginHolder<SolrRequestHandler> holder, PluginInfo info) {
     register(
         new LazyLoadedApi(HANDLER_NAME_SPEC_PROVIDER, holder),
-        Collections.singletonMap(HANDLER_NAME, info.attributes.get(NAME)));
+        Map.of(HANDLER_NAME, info.attributes.get(NAME)));
   }
 
   public static SpecProvider constructSpec(PluginInfo info) {
@@ -417,8 +416,7 @@ public static List<CommandOperation> getCommandOperations(
       ContentStream stream, Map<String, JsonSchemaValidator> validators, boolean validate) {
     List<CommandOperation> parsedCommands = null;
     try {
-      parsedCommands =
-          CommandOperation.readCommands(Collections.singleton(stream), new NamedList<>());
+      parsedCommands = CommandOperation.readCommands(Set.of(stream), new NamedList<>());
     } catch (IOException e) {
       throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "Unable to parse commands", e);
     }

solr/core/src/java/org/apache/solr/cli/CLIUtils.java

@@ -26,7 +26,7 @@
 import java.net.URISyntaxException;
 import java.nio.file.Path;
 import java.util.Arrays;
-import java.util.Collections;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
@@ -278,7 +278,7 @@ public static CloudSolrClient getCloudSolrClient(String zkHost) {
 
   public static CloudSolrClient getCloudSolrClient(
       String zkHost, HttpJettySolrClient.Builder builder) {
-    return new CloudSolrClient.Builder(Collections.singletonList(zkHost), Optional.empty())
+    return new CloudSolrClient.Builder(List.of(zkHost), Optional.empty())
         .withHttpClientBuilder(builder)
         .build();
   }

solr/core/src/java/org/apache/solr/cli/ExportTool.java

@@ -36,7 +36,6 @@
 import java.time.Instant;
 import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
@@ -247,9 +246,7 @@ void fetchUniqueKey() throws SolrServerException, IOException {
       var builder = new HttpJettySolrClient.Builder().withOptionalBasicAuthCredentials(credentials);
 
       solrClient =
-          new CloudSolrClient.Builder(Collections.singletonList(baseurl))
-              .withHttpClientBuilder(builder)
-              .build();
+          new CloudSolrClient.Builder(List.of(baseurl)).withHttpClientBuilder(builder).build();
       NamedList<Object> response =
           solrClient.request(
               new GenericSolrRequest(

solr/core/src/java/org/apache/solr/cli/RunExampleTool.java

@@ -28,8 +28,8 @@
 import java.nio.file.StandardCopyOption;
 import java.time.Duration;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
@@ -674,7 +674,7 @@ protected void runCloudExample(CommandLine cli) throws Exception {
   /** wait until the number of live nodes == numNodes. */
   protected void waitToSeeLiveNodes(String zkHost, int numNodes) {
     try (CloudSolrClient cloudClient =
-        new CloudSolrClient.Builder(Collections.singletonList(zkHost), Optional.empty()).build()) {
+        new CloudSolrClient.Builder(List.of(zkHost), Optional.empty()).build()) {
       Set<String> liveNodes = cloudClient.getClusterState().getLiveNodes();
       int numLiveNodes = (liveNodes != null) ? liveNodes.size() : 0;
       long timeoutNanos = System.nanoTime() + TimeUnit.NANOSECONDS.convert(10, TimeUnit.SECONDS);

solr/core/src/java/org/apache/solr/cloud/DistributedClusterStateUpdater.java

@@ -17,14 +17,12 @@
 
 package org.apache.solr.cloud;
 
-import static java.util.Collections.singletonMap;
 import static org.apache.solr.cloud.overseer.ZkStateWriter.NO_OP;
 import static org.apache.solr.common.cloud.ZkStateReader.COLLECTIONS_ZKNODE;
 
 import java.lang.invoke.MethodHandles;
 import java.time.Instant;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -548,7 +546,7 @@ private void doStateDotJsonCasUpdate(ClusterState updatedState)
       } else {
         // Collection update or creation
         DocCollection collection = updatedState.getCollection(updater.getCollectionName());
-        byte[] stateJson = Utils.toJSON(singletonMap(updater.getCollectionName(), collection));
+        byte[] stateJson = Utils.toJSON(Map.of(updater.getCollectionName(), collection));
 
         if (updater.isCollectionCreation()) {
           // The state.json file does not exist yet (more precisely it is assumed not to exist)
@@ -946,10 +944,7 @@ public void computeUpdates(ClusterState clusterState, SolrZkClient client) {
             (zkcmd != ZkStateWriter.NO_OP)
                 ? clusterState.copyWith(zkcmd.name, zkcmd.collection)
                 : null;
-        replicaOpsList =
-            (zkcmd.ops != null && zkcmd.ops.get() != null)
-                ? Collections.singletonList(zkcmd.ops)
-                : null;
+        replicaOpsList = (zkcmd.ops != null && zkcmd.ops.get() != null) ? List.of(zkcmd.ops) : null;
       } else {
         computedState = null;
         replicaOpsList = null;

solr/core/src/java/org/apache/solr/cloud/Overseer.java

@@ -24,7 +24,6 @@
 import java.io.IOException;
 import java.lang.invoke.MethodHandles;
 import java.util.ArrayDeque;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -510,40 +509,39 @@ private List<ZkWriteCommand> processMessage(
       if (collectionAction != null) {
         switch (collectionAction) {
           case CREATE:
-            return Collections.singletonList(
+            return List.of(
                 new ClusterStateMutator(getSolrCloudManager())
                     .createCollection(clusterState, message));
           case DELETE:
-            return Collections.singletonList(
+            return List.of(
                 new ClusterStateMutator(getSolrCloudManager())
                     .deleteCollection(clusterState, message));
           case CREATESHARD:
-            return Collections.singletonList(
+            return List.of(
                 new CollectionMutator(getSolrCloudManager()).createShard(clusterState, message));
           case DELETESHARD:
-            return Collections.singletonList(
+            return List.of(
                 new CollectionMutator(getSolrCloudManager()).deleteShard(clusterState, message));
           case ADDREPLICA:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).addReplica(clusterState, message));
           case ADDREPLICAPROP:
-            return Collections.singletonList(
+            return List.of(
                 new ReplicaMutator(getSolrCloudManager())
                     .addReplicaProperty(clusterState, message));
           case DELETEREPLICAPROP:
-            return Collections.singletonList(
+            return List.of(
                 new ReplicaMutator(getSolrCloudManager())
                     .deleteReplicaProperty(clusterState, message));
           case BALANCESHARDUNIQUE:
             ExclusiveSliceProperty dProp = new ExclusiveSliceProperty(clusterState, message);
             if (dProp.balanceProperty()) {
               String collName = message.getStr(ZkStateReader.COLLECTION_PROP);
-              return Collections.singletonList(
-                  new ZkWriteCommand(collName, dProp.getDocCollection()));
+              return List.of(new ZkWriteCommand(collName, dProp.getDocCollection()));
             }
             break;
           case MODIFYCOLLECTION:
-            return Collections.singletonList(
+            return List.of(
                 new CollectionMutator(getSolrCloudManager())
                     .modifyCollection(clusterState, message));
           default:
@@ -558,22 +556,22 @@ private List<ZkWriteCommand> processMessage(
         }
         switch (overseerAction) {
           case STATE:
-            return Collections.singletonList(
+            return List.of(
                 new ReplicaMutator(getSolrCloudManager()).setState(clusterState, message));
           case LEADER:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).setShardLeader(clusterState, message));
           case DELETECORE:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).removeReplica(clusterState, message));
           case ADDROUTINGRULE:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).addRoutingRule(clusterState, message));
           case REMOVEROUTINGRULE:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).removeRoutingRule(clusterState, message));
           case UPDATESHARDSTATE:
-            return Collections.singletonList(
+            return List.of(
                 new SliceMutator(getSolrCloudManager()).updateShardState(clusterState, message));
           case QUIT:
             if (myId.equals(message.get(ID))) {
@@ -594,7 +592,7 @@ private List<ZkWriteCommand> processMessage(
         }
       }
 
-      return Collections.singletonList(ZkStateWriter.NO_OP);
+      return List.of(ZkStateWriter.NO_OP);
     }
 
     private LeaderStatus amILeader() {

solr/core/src/java/org/apache/solr/cloud/api/collections/AddReplicaCmd.java

@@ -32,9 +32,9 @@
 import java.lang.invoke.MethodHandles;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
 import org.apache.solr.client.solrj.cloud.SolrCloudManager;
@@ -287,7 +287,7 @@ private ModifiableSolrParams getReplicaParams(
                 ccc.getZkStateReader(),
                 ccc.getSolrCloudManager().getTimeSource(),
                 collectionName,
-                Collections.singleton(createReplica.coreName))
+                Set.of(createReplica.coreName))
             .get(createReplica.coreName)
             .getName());
 

solr/core/src/java/org/apache/solr/cloud/api/collections/Assign.java

@@ -297,7 +297,7 @@ public static List<ReplicaPosition> getNodesForNewReplicas(
     AssignRequest assignRequest =
         new AssignRequestBuilder()
             .forCollection(collectionName)
-            .forShard(Collections.singletonList(shard))
+            .forShard(List.of(shard))
             .assignReplicas(numReplicas)
             .onNodes(createNodeList)
             .build();

solr/core/src/java/org/apache/solr/cloud/api/collections/CollectionHandlingUtils.java

@@ -376,7 +376,7 @@ static void cleanBackup(
       BackupRepository repository, URI backupUri, BackupId backupId, CollectionCommandContext ccc)
       throws Exception {
     new DeleteBackupCmd(ccc)
-        .deleteBackupIds(backupUri, repository, Collections.singleton(backupId), new NamedList<>());
+        .deleteBackupIds(backupUri, repository, Set.of(backupId), new NamedList<>());
   }
 
   static void deleteBackup(

solr/core/src/java/org/apache/solr/cloud/api/collections/CreateAliasCmd.java

@@ -19,7 +19,6 @@
 import static org.apache.solr.common.SolrException.ErrorCode.BAD_REQUEST;
 import static org.apache.solr.common.SolrException.ErrorCode.SERVER_ERROR;
 
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -179,8 +178,7 @@ private void ensureAliasCollection(
     // Create the collection
     createCollectionAndWait(
         adminCmdContext, aliasName, aliasProperties, initialCollectionName, ccc);
-    validateAllCollectionsExistAndNoDuplicates(
-        Collections.singletonList(initialCollectionName), zkStateReader);
+    validateAllCollectionsExistAndNoDuplicates(List.of(initialCollectionName), zkStateReader);
   }
 
   private void validateAllCollectionsExistAndNoDuplicates(