[SPARK-14868][BUILD] Enable NewLineAtEofChecker in checkstyle and fix lint-java errors

## What changes were proposed in this pull request?

Spark uses `NewLineAtEofChecker` rule in Scala by ScalaStyle. And, most Java code also comply with the rule. This PR aims to enforce the same rule `NewlineAtEndOfFile` by CheckStyle explicitly. Also, this fixes lint-java errors since SPARK-14465. The followings are the items.

- Adds a new line at the end of the files (19 files)
- Fixes 25 lint-java errors (12 RedundantModifier, 6 **ArrayTypeStyle**, 2 LineLength, 2 UnusedImports, 2 RegexpSingleline, 1 ModifierOrder)

## How was this patch tested?

After the Jenkins test succeeds, `dev/lint-java` should pass. (Currently, Jenkins dose not run lint-java.)
```bash
$ dev/lint-java
Using `mvn` from path: /usr/local/bin/mvn
Checkstyle checks passed.
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12632 from dongjoon-hyun/SPARK-14868.

core/src/main/java/org/apache/spark/api/java/function/package-info.java

@@ -20,4 +20,4 @@
  * these interfaces to pass functions to various Java API methods for Spark. Please visit Spark's
  * Java programming guide for more details.
  */
-package org.apache.spark.api.java.function;
\ No newline at end of file
+package org.apache.spark.api.java.function;

core/src/main/java/org/apache/spark/shuffle/sort/ShuffleExternalSorter.java

@@ -256,8 +256,8 @@ final class ShuffleExternalSorter extends MemoryConsumer {
     final long spillSize = freeMemory();
     inMemSorter.reset();
     // Reset the in-memory sorter's pointer array only after freeing up the memory pages holding the
-    // records. Otherwise, if the task is over allocated memory, then without freeing the memory pages,
-    // we might not be able to get memory for the pointer array.
+    // records. Otherwise, if the task is over allocated memory, then without freeing the memory
+    // pages, we might not be able to get memory for the pointer array.
     taskContext.taskMetrics().incMemoryBytesSpilled(spillSize);
     return spillSize;
   }

core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java

@@ -22,7 +22,6 @@ import com.google.common.primitives.UnsignedLongs;
 import org.apache.spark.annotation.Private;
 import org.apache.spark.unsafe.types.ByteArray;
 import org.apache.spark.unsafe.types.UTF8String;
-import org.apache.spark.util.Utils;
 
 @Private
 public class PrefixComparators {
@@ -69,7 +68,7 @@ public class PrefixComparators {
    * Provides radix sort parameters. Comparators implementing this also are indicating that the
    * ordering they define is compatible with radix sort.
    */
-  public static abstract class RadixSortSupport extends PrefixComparator {
+  public abstract static class RadixSortSupport extends PrefixComparator {
     /** @return Whether the sort should be descending in binary sort order. */
     public abstract boolean sortDescending();
 
@@ -82,37 +81,37 @@ public class PrefixComparators {
   //
 
   public static final class UnsignedPrefixComparator extends RadixSortSupport {
-    @Override public final boolean sortDescending() { return false; }
-    @Override public final boolean sortSigned() { return false; }
+    @Override public boolean sortDescending() { return false; }
+    @Override public boolean sortSigned() { return false; }
     @Override
-    public final int compare(long aPrefix, long bPrefix) {
+    public int compare(long aPrefix, long bPrefix) {
       return UnsignedLongs.compare(aPrefix, bPrefix);
     }
   }
 
   public static final class UnsignedPrefixComparatorDesc extends RadixSortSupport {
-    @Override public final boolean sortDescending() { return true; }
-    @Override public final boolean sortSigned() { return false; }
+    @Override public boolean sortDescending() { return true; }
+    @Override public boolean sortSigned() { return false; }
     @Override
-    public final int compare(long bPrefix, long aPrefix) {
+    public int compare(long bPrefix, long aPrefix) {
       return UnsignedLongs.compare(aPrefix, bPrefix);
     }
   }
 
   public static final class SignedPrefixComparator extends RadixSortSupport {
-    @Override public final boolean sortDescending() { return false; }
-    @Override public final boolean sortSigned() { return true; }
+    @Override public boolean sortDescending() { return false; }
+    @Override public boolean sortSigned() { return true; }
     @Override
-    public final int compare(long a, long b) {
+    public int compare(long a, long b) {
       return (a < b) ? -1 : (a > b) ? 1 : 0;
     }
   }
 
   public static final class SignedPrefixComparatorDesc extends RadixSortSupport {
-    @Override public final boolean sortDescending() { return true; }
-    @Override public final boolean sortSigned() { return true; }
+    @Override public boolean sortDescending() { return true; }
+    @Override public boolean sortSigned() { return true; }
     @Override
-    public final int compare(long b, long a) {
+    public int compare(long b, long a) {
       return (a < b) ? -1 : (a > b) ? 1 : 0;
     }
   }

core/src/main/java/org/apache/spark/util/collection/unsafe/sort/RadixSort.java

@@ -16,7 +16,7 @@
  */
 
 package org.apache.spark.util.collection.unsafe.sort;
- 
+
 import org.apache.spark.unsafe.Platform;
 import org.apache.spark.unsafe.array.LongArray;
 
@@ -227,7 +227,7 @@ public class RadixSort {
     }
     return counts;
   }
-  
+
   /**
    * Specialization of sortAtByte() for key-prefix arrays.
    */

core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeExternalSorter.java

@@ -212,8 +212,8 @@ public final class UnsafeExternalSorter extends MemoryConsumer {
     // written to disk. This also counts the space needed to store the sorter's pointer array.
     inMemSorter.reset();
     // Reset the in-memory sorter's pointer array only after freeing up the memory pages holding the
-    // records. Otherwise, if the task is over allocated memory, then without freeing the memory pages,
-    // we might not be able to get memory for the pointer array.
+    // records. Otherwise, if the task is over allocated memory, then without freeing the memory
+    // pages, we might not be able to get memory for the pointer array.
 
     taskContext.taskMetrics().incMemoryBytesSpilled(spillSize);
     totalSpillBytes += spillSize;

core/src/main/scala/org/apache/spark/annotation/package-info.java

@@ -20,4 +20,4 @@
  * This package consist of these annotations, which are used project wide and are reflected in
  * Scala and Java docs.
  */
-package org.apache.spark.annotation;
\ No newline at end of file
+package org.apache.spark.annotation;

core/src/main/scala/org/apache/spark/api/java/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Spark Java programming APIs.
  */
-package org.apache.spark.api.java;
\ No newline at end of file
+package org.apache.spark.api.java;

core/src/main/scala/org/apache/spark/broadcast/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Spark's broadcast variables, used to broadcast immutable datasets to all nodes.
  */
-package org.apache.spark.broadcast;
\ No newline at end of file
+package org.apache.spark.broadcast;

core/src/main/scala/org/apache/spark/executor/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Package for executor components used with various cluster managers.
  */
-package org.apache.spark.executor;
\ No newline at end of file
+package org.apache.spark.executor;

core/src/main/scala/org/apache/spark/io/package-info.java

@@ -18,4 +18,4 @@
 /**
  * IO codecs used for compression.
  */
-package org.apache.spark.io;
\ No newline at end of file
+package org.apache.spark.io;

core/src/main/scala/org/apache/spark/rdd/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Provides implementation's of various RDDs.
  */
-package org.apache.spark.rdd;
\ No newline at end of file
+package org.apache.spark.rdd;

core/src/main/scala/org/apache/spark/scheduler/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Spark's DAG scheduler.
  */
-package org.apache.spark.scheduler;
\ No newline at end of file
+package org.apache.spark.scheduler;

core/src/main/scala/org/apache/spark/util/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Spark utilities.
  */
-package org.apache.spark.util;
\ No newline at end of file
+package org.apache.spark.util;

core/src/main/scala/org/apache/spark/util/random/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Utilities for random number generation.
  */
-package org.apache.spark.util.random;
\ No newline at end of file
+package org.apache.spark.util.random;

dev/checkstyle.xml

@@ -64,6 +64,8 @@
         <property name="message" value="No trailing whitespace allowed."/>
     </module>
 
+    <module name="NewlineAtEndOfFile"/>
+
     <module name="TreeWalker">
         <module name="OuterTypeFilename"/>
         <module name="IllegalTokenText">

external/flume/src/main/scala/org/apache/spark/streaming/flume/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Spark streaming receiver for Flume.
  */
-package org.apache.spark.streaming.flume;
\ No newline at end of file
+package org.apache.spark.streaming.flume;

external/kafka/src/main/scala/org/apache/spark/streaming/kafka/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Kafka receiver for spark streaming.
  */
-package org.apache.spark.streaming.kafka;
\ No newline at end of file
+package org.apache.spark.streaming.kafka;

external/kinesis-asl/src/main/resources/log4j.properties

@@ -34,4 +34,4 @@ log4j.appender.console.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{1}:
 log4j.logger.org.spark_project.jetty=WARN
 log4j.logger.org.spark_project.jetty.util.component.AbstractLifeCycle=ERROR
 log4j.logger.org.apache.spark.repl.SparkIMain$exprTyper=INFO
-log4j.logger.org.apache.spark.repl.SparkILoop$SparkILoopInterpreter=INFO
\ No newline at end of file
+log4j.logger.org.apache.spark.repl.SparkILoop$SparkILoopInterpreter=INFO

graphx/src/main/scala/org/apache/spark/graphx/package-info.java

@@ -19,4 +19,4 @@
  * ALPHA COMPONENT
  * GraphX is a graph processing framework built on top of Spark.
  */
-package org.apache.spark.graphx;
\ No newline at end of file
+package org.apache.spark.graphx;

graphx/src/main/scala/org/apache/spark/graphx/util/package-info.java

@@ -18,4 +18,4 @@
 /**
  * Collections of utilities used by graphx.
  */
-package org.apache.spark.graphx.util;
\ No newline at end of file
+package org.apache.spark.graphx.util;