[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.

2 files changed, 4 insertions, 4 deletions

diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
index 6b2c48ef1c..b2df79ba74 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
@@ -58,7 +58,7 @@ public class JavaStringIndexerSuite {
       createStructField("label", StringType, false)
     });
     List<Row> data = Arrays.asList(
-      c(0, "a"), c(1, "b"), c(2, "c"), c(3, "a"), c(4, "a"), c(5, "c"));
+      cr(0, "a"), cr(1, "b"), cr(2, "c"), cr(3, "a"), cr(4, "a"), cr(5, "c"));
     DataFrame dataset = sqlContext.createDataFrame(data, schema);
 
     StringIndexer indexer = new StringIndexer()
@@ -67,12 +67,12 @@ public class JavaStringIndexerSuite {
     DataFrame output = indexer.fit(dataset).transform(dataset);
 
     Assert.assertArrayEquals(
-      new Row[] { c(0, 0.0), c(1, 2.0), c(2, 1.0), c(3, 0.0), c(4, 0.0), c(5, 1.0) },
+      new Row[] { cr(0, 0.0), cr(1, 2.0), cr(2, 1.0), cr(3, 0.0), cr(4, 0.0), cr(5, 1.0) },
       output.orderBy("id").select("id", "labelIndex").collect());
   }
 
   /** An alias for RowFactory.create. */
-  private Row c(Object... values) {
+  private Row cr(Object... values) {
     return RowFactory.create(values);
   }
 }
diff --git a/mllib/src/test/java/org/apache/spark/mllib/clustering/JavaLDASuite.java b/mllib/src/test/java/org/apache/spark/mllib/clustering/JavaLDASuite.java
index 3fea359a3b..225a216270 100644
--- a/mllib/src/test/java/org/apache/spark/mllib/clustering/JavaLDASuite.java
+++ b/mllib/src/test/java/org/apache/spark/mllib/clustering/JavaLDASuite.java
@@ -144,7 +144,7 @@ public class JavaLDASuite implements Serializable {
   }
 
   @Test
-  public void OnlineOptimizerCompatibility() {
+  public void onlineOptimizerCompatibility() {
     int k = 3;
     double topicSmoothing = 1.2;
     double termSmoothing = 1.2;