Replace explicit type conversion with instanceof pattern variable in server module

server/src/main/java/org/opensearch/action/ActionModule.java

@@ -847,11 +847,11 @@ public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {
         List<AbstractCatAction> catActions = new ArrayList<>();
         List<AbstractListAction> listActions = new ArrayList<>();
         Consumer<RestHandler> registerHandler = handler -> {
-            if (handler instanceof AbstractCatAction) {
-                if (handler instanceof AbstractListAction && ((AbstractListAction) handler).isActionPaginated()) {
-                    listActions.add((AbstractListAction) handler);
+            if (handler instanceof AbstractCatAction abstractCatAction) {
+                if (handler instanceof AbstractListAction abstractListAction && abstractListAction.isActionPaginated()) {
+                    listActions.add(abstractListAction);
                 } else {
-                    catActions.add((AbstractCatAction) handler);
+                    catActions.add(abstractCatAction);
                 }
             }
             restController.registerHandler(handler);
@@ -1265,8 +1265,8 @@ public void unregisterDynamicRoute(NamedRoute route) {
          * @return the corresponding {@link RestSendToExtensionAction} if it is registered, null otherwise.
          */
         public RestSendToExtensionAction get(RestHandler.Route route) {
-            if (route instanceof NamedRoute) {
-                return routeRegistry.get((NamedRoute) route);
+            if (route instanceof NamedRoute namedRoute) {
+                return routeRegistry.get(namedRoute);
             }
             // Only NamedRoutes are map keys so any other route is not in the map
             return null;

server/src/main/java/org/opensearch/action/ActionType.java

@@ -82,7 +82,7 @@ public TransportRequestOptions transportOptions(Settings settings) {
 
     @Override
     public boolean equals(Object o) {
-        return o instanceof ActionType && name.equals(((ActionType<?>) o).name());
+        return o instanceof ActionType<?> actionType && name.equals(actionType.name());
     }
 
     @Override

server/src/main/java/org/opensearch/action/bulk/TransportBulkAction.java

@@ -223,10 +223,9 @@ public TransportBulkAction(
      */
     public static IndexRequest getIndexWriteRequest(DocWriteRequest<?> docWriteRequest) {
         IndexRequest indexRequest = null;
-        if (docWriteRequest instanceof IndexRequest) {
-            indexRequest = (IndexRequest) docWriteRequest;
-        } else if (docWriteRequest instanceof UpdateRequest) {
-            UpdateRequest updateRequest = (UpdateRequest) docWriteRequest;
+        if (docWriteRequest instanceof IndexRequest indexReq) {
+            indexRequest = indexReq;
+        } else if (docWriteRequest instanceof UpdateRequest updateRequest) {
             indexRequest = updateRequest.docAsUpsert() ? updateRequest.doc() : updateRequest.upsertRequest();
         }
         return indexRequest;

server/src/main/java/org/opensearch/bootstrap/StartupException.java

@@ -81,8 +81,8 @@ public void printStackTrace(PrintWriter s) {
     private void printStackTrace(Consumer<String> consumer) {
         Throwable originalCause = getCause();
         Throwable cause = originalCause;
-        if (cause instanceof CreationException) {
-            cause = getFirstGuiceCause((CreationException) cause);
+        if (cause instanceof CreationException creationException) {
+            cause = getFirstGuiceCause(creationException);
         }
 
         if (cause != null) {

server/src/main/java/org/opensearch/cluster/InternalClusterInfoService.java

@@ -569,8 +569,7 @@ public void onFailure(Exception e) {
 
         @Override
         public void onRejection(Exception e) {
-            final boolean shutDown = e instanceof OpenSearchRejectedExecutionException
-                && ((OpenSearchRejectedExecutionException) e).isExecutorShutdown();
+            final boolean shutDown = e instanceof OpenSearchRejectedExecutionException osre && osre.isExecutorShutdown();
             logger.log(shutDown ? Level.DEBUG : Level.WARN, "refreshing cluster info rejected [{}]", reason, e);
         }
     }

server/src/main/java/org/opensearch/common/inject/internal/Errors.java

@@ -352,15 +352,12 @@ public void exposedButNotBound(Key<?> key) {
     }
 
     public static Collection<Message> getMessagesFromThrowable(Throwable throwable) {
-        if (throwable instanceof ProvisionException) {
-            return ((ProvisionException) throwable).getErrorMessages();
-        } else if (throwable instanceof ConfigurationException) {
-            return ((ConfigurationException) throwable).getErrorMessages();
-        } else if (throwable instanceof CreationException) {
-            return ((CreationException) throwable).getErrorMessages();
-        } else {
-            return emptySet();
-        }
+        return switch (throwable) {
+            case ProvisionException provisionException -> provisionException.getErrorMessages();
+            case ConfigurationException configurationException -> configurationException.getErrorMessages();
+            case CreationException creationException -> creationException.getErrorMessages();
+            default -> emptySet();
+        };
     }
 
     public Errors errorInUserCode(Throwable cause, String messageFormat, Object... arguments) {
@@ -649,29 +646,27 @@ public static Object convert(Object o) {
     }
 
     public static void formatSource(Formatter formatter, Object source) {
-        if (source instanceof Dependency) {
-            Dependency<?> dependency = (Dependency<?>) source;
+        if (source instanceof Dependency<?> dependency) {
             InjectionPoint injectionPoint = dependency.getInjectionPoint();
             if (injectionPoint != null) {
                 formatInjectionPoint(formatter, dependency, injectionPoint);
             } else {
                 formatSource(formatter, dependency.getKey());
             }
 
-        } else if (source instanceof InjectionPoint) {
-            formatInjectionPoint(formatter, null, (InjectionPoint) source);
+        } else if (source instanceof InjectionPoint injectionPoint) {
+            formatInjectionPoint(formatter, null, injectionPoint);
 
-        } else if (source instanceof Class) {
-            formatter.format("  at %s%n", StackTraceElements.forType((Class<?>) source));
+        } else if (source instanceof Class<?> clazz) {
+            formatter.format("  at %s%n", StackTraceElements.forType(clazz));
 
-        } else if (source instanceof Member) {
-            formatter.format("  at %s%n", StackTraceElements.forMember((Member) source));
+        } else if (source instanceof Member member) {
+            formatter.format("  at %s%n", StackTraceElements.forMember(member));
 
         } else if (source instanceof TypeLiteral) {
             formatter.format("  while locating %s%n", source);
 
-        } else if (source instanceof Key) {
-            Key<?> key = (Key<?>) source;
+        } else if (source instanceof Key<?> key) {
             formatter.format("  while locating %s%n", convert(key));
 
         } else {