Fix checkstyle.

Author: szetszwo

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java

@@ -736,7 +736,7 @@ public class CommonConfigurationKeysPublic {
    */
   public static final String  HADOOP_RPC_PROTECTION =
     "hadoop.rpc.protection";
-  public static String HADOOP_SECURITY_SASL_CUSTOMIZEDCALLBACKHANDLER_CLASS_KEY
+  public static final String HADOOP_SECURITY_SASL_CUSTOMIZEDCALLBACKHANDLER_CLASS_KEY
       = "hadoop.security.sasl.CustomizedCallbackHandler.class";
   /** Class to override Sasl Properties for a connection */
   public static final String  HADOOP_SECURITY_SASL_PROPS_RESOLVER_CLASS =

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/CustomizedCallbackHandler.java

@@ -37,7 +37,8 @@ public interface CustomizedCallbackHandler {
   class Cache {
     private static final Map<String, CustomizedCallbackHandler> MAP = new HashMap<>();
 
-    private static synchronized CustomizedCallbackHandler getSynchronously(String key, Configuration conf) {
+    private static synchronized CustomizedCallbackHandler getSynchronously(
+        String key, Configuration conf) {
       //check again synchronously
       final CustomizedCallbackHandler cached = MAP.get(key);
       if (cached != null) {
@@ -68,6 +69,8 @@ private static CustomizedCallbackHandler get(String key, Configuration conf) {
     public static synchronized void clear() {
       MAP.clear();
     }
+
+    private Cache() { }
   }
 
   class DefaultHandler implements CustomizedCallbackHandler {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/package-info.java

@@ -0,0 +1,22 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Classes for hadoop security.
+ */
+package org.apache.hadoop.security;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/sasl/package-info.java

@@ -0,0 +1,22 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Classes for data transfer SASL implementation.
+ */
+package org.apache.hadoop.hdfs.protocol.datatransfer.sasl;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/protocol/datatransfer/sasl/TestCustomizedCallbackHandler.java

@@ -18,7 +18,6 @@
 package org.apache.hadoop.hdfs.protocol.datatransfer.sasl;
 
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.protocol.datatransfer.sasl.SaslDataTransferServer.SaslServerCallbackHandler;
 import org.apache.hadoop.security.CustomizedCallbackHandler;
@@ -35,6 +34,8 @@
 import java.util.List;
 import java.util.concurrent.atomic.AtomicReference;
 
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_SASL_CUSTOMIZEDCALLBACKHANDLER_CLASS_KEY;
+
 /** For testing {@link CustomizedCallbackHandler}. */
 public class TestCustomizedCallbackHandler {
   static final Logger LOG = LoggerFactory.getLogger(TestCustomizedCallbackHandler.class);
@@ -87,7 +88,7 @@ public void testCustomizedCallbackHandler() throws Exception {
     assertCallbacks(callbacks);
 
     reset();
-    conf.setClass(CommonConfigurationKeysPublic.HADOOP_SECURITY_SASL_CUSTOMIZEDCALLBACKHANDLER_CLASS_KEY,
+    conf.setClass(HADOOP_SECURITY_SASL_CUSTOMIZEDCALLBACKHANDLER_CLASS_KEY,
         MyCallbackHandler.class, CustomizedCallbackHandler.class);
     new SaslRpcServer.SaslDigestCallbackHandler(null, null, conf).handle(callbacks);
     assertCallbacks(callbacks);