[SPARK-6990][BUILD] Add Java linting script; fix minor warnings

This replaces https://github.com/apache/spark/pull/9696

Invoke Checkstyle and print any errors to the console, failing the step.
Use Google's style rules modified according to
https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide
Some important checks are disabled (see TODOs in `checkstyle.xml`) due to
multiple violations being present in the codebase.

Suggest fixing those TODOs in a separate PR(s).

More on Checkstyle can be found on the [official website](http://checkstyle.sourceforge.net/).

Sample output (from [build 46345](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/46345/consoleFull)) (duplicated because I run the build twice with different profiles):

> Checkstyle checks failed at following occurrences:
[ERROR] src/main/java/org/apache/spark/sql/execution/datasources/parquet/UnsafeRowParquetRecordReader.java:[217,7] (coding) MissingSwitchDefault: switch without "default" clause.
> [ERROR] src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java:[198,10] (modifier) ModifierOrder: 'protected' modifier out of order with the JLS suggestions.
> [ERROR] src/main/java/org/apache/spark/sql/execution/datasources/parquet/UnsafeRowParquetRecordReader.java:[217,7] (coding) MissingSwitchDefault: switch without "default" clause.
> [ERROR] src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java:[198,10] (modifier) ModifierOrder: 'protected' modifier out of order with the JLS suggestions.
> [error] running /home/jenkins/workspace/SparkPullRequestBuilder2/dev/lint-java ; received return code 1

Also fix some of the minor violations that didn't require sweeping changes.

Apologies for the previous botched PRs - I finally figured out the issue.

cr: JoshRosen, pwendell

> I state that the contribution is my original work, and I license the work to the project under the project's open source license.

Author: Dmitry Erastov <derastov@gmail.com>

Closes #9867 from dskrvk/master.

3 files changed, 8 insertions, 8 deletions

diff --git a/streaming/src/main/java/org/apache/spark/streaming/util/WriteAheadLog.java b/streaming/src/main/java/org/apache/spark/streaming/util/WriteAheadLog.java
index 3738fc1a23..2803cad809 100644
--- a/streaming/src/main/java/org/apache/spark/streaming/util/WriteAheadLog.java
+++ b/streaming/src/main/java/org/apache/spark/streaming/util/WriteAheadLog.java
@@ -37,26 +37,26 @@ public abstract class WriteAheadLog {
    * ensure that the written data is durable and readable (using the record handle) by the
    * time this function returns.
    */
-  abstract public WriteAheadLogRecordHandle write(ByteBuffer record, long time);
+  public abstract WriteAheadLogRecordHandle write(ByteBuffer record, long time);
 
   /**
    * Read a written record based on the given record handle.
    */
-  abstract public ByteBuffer read(WriteAheadLogRecordHandle handle);
+  public abstract ByteBuffer read(WriteAheadLogRecordHandle handle);
 
   /**
    * Read and return an iterator of all the records that have been written but not yet cleaned up.
    */
-  abstract public Iterator<ByteBuffer> readAll();
+  public abstract Iterator<ByteBuffer> readAll();
 
   /**
    * Clean all the records that are older than the threshold time. It can wait for
    * the completion of the deletion.
    */
-  abstract public void clean(long threshTime, boolean waitForCompletion);
+  public abstract void clean(long threshTime, boolean waitForCompletion);
 
   /**
    * Close this log and release any resources.
    */
-  abstract public void close();
+  public abstract void close();
 }
diff --git a/streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java b/streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java
index 609bb4413b..9722c60bba 100644
--- a/streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java
+++ b/streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java
@@ -1332,12 +1332,12 @@ public class JavaAPISuite extends LocalJavaStreamingContext implements Serializa
   public void testUpdateStateByKeyWithInitial() {
     List<List<Tuple2<String, Integer>>> inputData = stringIntKVStream;
 
-    List<Tuple2<String, Integer>> initial = Arrays.asList (
+    List<Tuple2<String, Integer>> initial = Arrays.asList(
         new Tuple2<>("california", 1),
             new Tuple2<>("new york", 2));
 
     JavaRDD<Tuple2<String, Integer>> tmpRDD = ssc.sparkContext().parallelize(initial);
-    JavaPairRDD<String, Integer> initialRDD = JavaPairRDD.fromJavaRDD (tmpRDD);
+    JavaPairRDD<String, Integer> initialRDD = JavaPairRDD.fromJavaRDD(tmpRDD);
 
     List<List<Tuple2<String, Integer>>> expected = Arrays.asList(
         Arrays.asList(new Tuple2<>("california", 5),
diff --git a/streaming/src/test/java/org/apache/spark/streaming/JavaTrackStateByKeySuite.java b/streaming/src/test/java/org/apache/spark/streaming/JavaTrackStateByKeySuite.java
index eac4cdd14a..89d0bb7b61 100644
--- a/streaming/src/test/java/org/apache/spark/streaming/JavaTrackStateByKeySuite.java
+++ b/streaming/src/test/java/org/apache/spark/streaming/JavaTrackStateByKeySuite.java
@@ -95,7 +95,7 @@ public class JavaTrackStateByKeySuite extends LocalJavaStreamingContext implemen
 
     JavaTrackStateDStream<String, Integer, Boolean, Double> stateDstream2 =
         wordsDstream.trackStateByKey(
-            StateSpec.<String, Integer, Boolean, Double> function(trackStateFunc2)
+            StateSpec.<String, Integer, Boolean, Double>function(trackStateFunc2)
                 .initialState(initialRDD)
                 .numPartitions(10)
                 .partitioner(new HashPartitioner(10))