[hotfix] Apply fixes to satisfy Checkstyle 9+

Author: snuyanzin

flink-core/src/main/java/org/apache/flink/api/common/operators/util/ListKeyGroupedIterator.java

@@ -64,7 +64,7 @@ public ListKeyGroupedIterator(
         this.serializer = serializer;
         this.comparator = comparator;
 
-        this.done = input.isEmpty() ? true : false;
+        this.done = input.isEmpty();
     }
 
     /**

flink-core/src/main/java/org/apache/flink/core/memory/ByteArrayOutputStreamWithPos.java

@@ -88,7 +88,7 @@ public void reset() {
         count = 0;
     }
 
-    public byte toByteArray()[] {
+    public byte[] toByteArray() {
         return Arrays.copyOf(buffer, count);
     }
 

flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/channel/SequentialChannelStateReader.java

@@ -1,4 +1,3 @@
-package org.apache.flink.runtime.checkpoint.channel;
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -16,6 +15,8 @@
  * limitations under the License.
  */
 
+package org.apache.flink.runtime.checkpoint.channel;
+
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.runtime.io.network.api.writer.ResultPartitionWriter;
 import org.apache.flink.runtime.io.network.partition.consumer.InputGate;

flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/job/JobPlanHandler.java

@@ -1,4 +1,3 @@
-package org.apache.flink.runtime.rest.handler.job;
 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
@@ -17,6 +16,8 @@
  * limitations under the License.
  */
 
+package org.apache.flink.runtime.rest.handler.job;
+
 import org.apache.flink.api.common.time.Time;
 import org.apache.flink.runtime.executiongraph.AccessExecutionGraph;
 import org.apache.flink.runtime.rest.handler.HandlerRequest;

flink-state-backends/flink-statebackend-changelog/src/main/java/org/apache/flink/state/changelog/ChangelogState.java

@@ -1,4 +1,3 @@
-package org.apache.flink.state.changelog;
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -16,6 +15,8 @@
  * limitations under the License.
  */
 
+package org.apache.flink.state.changelog;
+
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.state.changelog.restore.ChangelogApplierFactory;
 import org.apache.flink.state.changelog.restore.StateChangeApplier;

flink-table/flink-sql-gateway/src/main/java/org/apache/flink/table/gateway/service/operation/OperationExecutor.java

@@ -783,7 +783,7 @@ public ResultFetcher callShowJobsOperation(
      * @param handle the specified operation handle
      * @param clusterAction the cluster action to run against the retrieved {@link ClusterClient}.
      * @param <ClusterID> type of the cluster id
-     * @param <Result>> type of the result
+     * @param <Result> type of the result
      * @throws SqlExecutionException if something goes wrong
      */
     private <ClusterID, Result> Result runClusterAction(