[SPARK-14011][CORE][SQL] Enable `LineLength` Java checkstyle rule

## What changes were proposed in this pull request?

[Spark Coding Style Guide](https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide) has 100-character limit on lines, but it's disabled for Java since 11/09/15. This PR enables **LineLength** checkstyle again. To help that, this also introduces **RedundantImport** and **RedundantModifier**, too. The following is the diff on `checkstyle.xml`.

```xml
-        <!-- TODO: 11/09/15 disabled - the lengths are currently > 100 in many places -->
-        <!--
         <module name="LineLength">
             <property name="max" value="100"/>
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
-        -->
         <module name="NoLineWrap"/>
         <module name="EmptyBlock">
             <property name="option" value="TEXT"/>
 -167,5 +164,7
         </module>
         <module name="CommentsIndentation"/>
         <module name="UnusedImports"/>
+        <module name="RedundantImport"/>
+        <module name="RedundantModifier"/>
```

## How was this patch tested?

Currently, `lint-java` is disabled in Jenkins. It needs a manual test.
After passing the Jenkins tests, `dev/lint-java` should passes locally.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11831 from dongjoon-hyun/SPARK-14011.

12 files changed, 16 insertions, 21 deletions

diff --git a/common/network-common/src/main/java/org/apache/spark/network/TransportContext.java b/common/network-common/src/main/java/org/apache/spark/network/TransportContext.java
index 238710d172..5320b28bc0 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/TransportContext.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/TransportContext.java
@@ -43,7 +43,8 @@ import org.apache.spark.network.util.TransportFrameDecoder;
 
 /**
  * Contains the context to create a {@link TransportServer}, {@link TransportClientFactory}, and to
- * setup Netty Channel pipelines with a {@link org.apache.spark.network.server.TransportChannelHandler}.
+ * setup Netty Channel pipelines with a
+ * {@link org.apache.spark.network.server.TransportChannelHandler}.
  *
  * There are two communication protocols that the TransportClient provides, control-plane RPCs and
  * data-plane "chunk fetching". The handling of the RPCs is performed outside of the scope of the
diff --git a/common/network-common/src/main/java/org/apache/spark/network/client/StreamCallback.java b/common/network-common/src/main/java/org/apache/spark/network/client/StreamCallback.java
index 29e6a30dc1..d322aec287 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/client/StreamCallback.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/client/StreamCallback.java
@@ -21,9 +21,9 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 
 /**
- * Callback for streaming data. Stream data will be offered to the {@link #onData(String, ByteBuffer)}
- * method as it arrives. Once all the stream data is received, {@link #onComplete(String)} will be
- * called.
+ * Callback for streaming data. Stream data will be offered to the
+ * {@link #onData(String, ByteBuffer)} method as it arrives. Once all the stream data is received,
+ * {@link #onComplete(String)} will be called.
  * <p>
  * The network library guarantees that a single thread will call these methods at a time, but
  * different call may be made by different threads.
diff --git a/common/network-common/src/main/java/org/apache/spark/network/client/TransportClientFactory.java b/common/network-common/src/main/java/org/apache/spark/network/client/TransportClientFactory.java
index 1008c67de3..f179bad1f4 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/client/TransportClientFactory.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/client/TransportClientFactory.java
@@ -64,7 +64,7 @@ public class TransportClientFactory implements Closeable {
     TransportClient[] clients;
     Object[] locks;
 
-    public ClientPool(int size) {
+    ClientPool(int size) {
       clients = new TransportClient[size];
       locks = new Object[size];
       for (int i = 0; i < size; i++) {
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/Message.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/Message.java
index 66f5b8b3a5..434935a8ef 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/Message.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/Message.java
@@ -33,7 +33,7 @@ public interface Message extends Encodable {
   boolean isBodyInFrame();
 
   /** Preceding every serialized Message is its type, which allows us to deserialize it. */
-  public static enum Type implements Encodable {
+  enum Type implements Encodable {
     ChunkFetchRequest(0), ChunkFetchSuccess(1), ChunkFetchFailure(2),
     RpcRequest(3), RpcResponse(4), RpcFailure(5),
     StreamRequest(6), StreamResponse(7), StreamFailure(8),
@@ -41,7 +41,7 @@ public interface Message extends Encodable {
 
     private final byte id;
 
-    private Type(int id) {
+    Type(int id) {
       assert id < 128 : "Cannot have more than 128 message types";
       this.id = (byte) id;
     }
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/RequestMessage.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/RequestMessage.java
index 31b15bb17a..b85171ed6f 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/RequestMessage.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/RequestMessage.java
@@ -17,8 +17,6 @@
 
 package org.apache.spark.network.protocol;
 
-import org.apache.spark.network.protocol.Message;
-
 /** Messages from the client to the server. */
 public interface RequestMessage extends Message {
   // token interface
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/ResponseMessage.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/ResponseMessage.java
index 6edffd11cf..194e6d9aa2 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/ResponseMessage.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/ResponseMessage.java
@@ -17,8 +17,6 @@
 
 package org.apache.spark.network.protocol;
 
-import org.apache.spark.network.protocol.Message;
-
 /** Messages from the server to the client. */
 public interface ResponseMessage extends Message {
   // token interface
diff --git a/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslMessage.java b/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslMessage.java
index e52b526f09..7331c2b481 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslMessage.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslMessage.java
@@ -36,11 +36,11 @@ class SaslMessage extends AbstractMessage {
 
   public final String appId;
 
-  public SaslMessage(String appId, byte[] message) {
+  SaslMessage(String appId, byte[] message) {
     this(appId, Unpooled.wrappedBuffer(message));
   }
 
-  public SaslMessage(String appId, ByteBuf message) {
+  SaslMessage(String appId, ByteBuf message) {
     super(new NettyManagedBuffer(message), true);
     this.appId = appId;
   }
diff --git a/common/network-common/src/main/java/org/apache/spark/network/server/OneForOneStreamManager.java b/common/network-common/src/main/java/org/apache/spark/network/server/OneForOneStreamManager.java
index ea9e735e0a..e2222ae085 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/server/OneForOneStreamManager.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/server/OneForOneStreamManager.java
@@ -32,8 +32,8 @@ import org.apache.spark.network.buffer.ManagedBuffer;
 import org.apache.spark.network.client.TransportClient;
 
 /**
- * StreamManager which allows registration of an Iterator&lt;ManagedBuffer&gt;, which are individually
- * fetched as chunks by the client. Each registered buffer is one chunk.
+ * StreamManager which allows registration of an Iterator&lt;ManagedBuffer&gt;, which are
+ * individually fetched as chunks by the client. Each registered buffer is one chunk.
  */
 public class OneForOneStreamManager extends StreamManager {
   private final Logger logger = LoggerFactory.getLogger(OneForOneStreamManager.class);
diff --git a/common/network-common/src/main/java/org/apache/spark/network/server/TransportChannelHandler.java b/common/network-common/src/main/java/org/apache/spark/network/server/TransportChannelHandler.java
index 18a9b7887e..f2223379a9 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/server/TransportChannelHandler.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/server/TransportChannelHandler.java
@@ -141,8 +141,8 @@ public class TransportChannelHandler extends SimpleChannelInboundHandler<Message
           if (responseHandler.numOutstandingRequests() > 0) {
             String address = NettyUtils.getRemoteAddress(ctx.channel());
             logger.error("Connection to {} has been quiet for {} ms while there are outstanding " +
-              "requests. Assuming connection is dead; please adjust spark.network.timeout if this " +
-              "is wrong.", address, requestTimeoutNs / 1000 / 1000);
+              "requests. Assuming connection is dead; please adjust spark.network.timeout if " +
+              "this is wrong.", address, requestTimeoutNs / 1000 / 1000);
             client.timeOut();
             ctx.close();
           } else if (closeIdleConnections) {
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/ByteUnit.java b/common/network-common/src/main/java/org/apache/spark/network/util/ByteUnit.java
index a2f018373f..e097714bbc 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/ByteUnit.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/ByteUnit.java
@@ -24,7 +24,7 @@ public enum ByteUnit {
   TiB ((long) Math.pow(1024L, 4L)),
   PiB ((long) Math.pow(1024L, 5L));
 
-  private ByteUnit(long multiplier) {
+  ByteUnit(long multiplier) {
     this.multiplier = multiplier;
   }
 
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/SystemPropertyConfigProvider.java b/common/network-common/src/main/java/org/apache/spark/network/util/SystemPropertyConfigProvider.java
index 5f20b70678..f15ec8d294 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/SystemPropertyConfigProvider.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/SystemPropertyConfigProvider.java
@@ -19,8 +19,6 @@ package org.apache.spark.network.util;
 
 import java.util.NoSuchElementException;
 
-import org.apache.spark.network.util.ConfigProvider;
-
 /** Uses System properties to obtain config values. */
 public class SystemPropertyConfigProvider extends ConfigProvider {
   @Override
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java b/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
index 3f7024a6aa..bd1830e6ab 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
@@ -205,7 +205,7 @@ public class TransportFrameDecoder extends ChannelInboundHandlerAdapter {
     return interceptor != null;
   }
 
-  public static interface Interceptor {
+  public interface Interceptor {
 
     /**
      * Handles data received from the remote end.