[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.

31 files changed, 368 insertions, 70 deletions

diff --git a/checkstyle-suppressions.xml b/checkstyle-suppressions.xml
new file mode 100644
index 0000000000..9242be3d03
--- /dev/null
+++ b/checkstyle-suppressions.xml
@@ -0,0 +1,33 @@
+<!--
+  ~ 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.
+  -->
+
+<!DOCTYPE suppressions PUBLIC
+"-//Puppy Crawl//DTD Suppressions 1.1//EN"
+"http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+
+<!--
+
+    This file contains suppression rules for Checkstyle checks.
+    Ideally only files that cannot be modified (e.g. third-party code)
+    should be added here. All other violations should be fixed.
+
+-->
+
+<suppressions>
+<suppress checks=".*"
+  files="core/src/main/java/org/apache/spark/util/collection/TimSort.java"/>
+</suppressions>
diff --git a/checkstyle.xml b/checkstyle.xml
new file mode 100644
index 0000000000..a493ee443c
--- /dev/null
+++ b/checkstyle.xml
@@ -0,0 +1,164 @@
+<!--
+  ~ 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.
+  -->
+
+<!DOCTYPE module PUBLIC
+          "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+          "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<!--
+
+    Checkstyle configuration based on the Google coding conventions from:
+
+    -  Google Java Style
+       https://google-styleguide.googlecode.com/svn-history/r130/trunk/javaguide.html
+
+    with Spark-specific changes from:
+
+    https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide
+
+    Checkstyle is very configurable. Be sure to read the documentation at
+    http://checkstyle.sf.net (or in your downloaded distribution).
+
+    Most Checks are configurable, be sure to consult the documentation.
+
+    To completely disable a check, just comment it out or delete it from the file.
+
+    Authors: Max Vetrenko, Ruslan Diachenko, Roman Ivanov.
+
+ -->
+
+<module name = "Checker">
+    <property name="charset" value="UTF-8"/>
+
+    <property name="severity" value="error"/>
+
+    <property name="fileExtensions" value="java, properties, xml"/>
+
+    <module name="SuppressionFilter">
+      <property name="file" value="checkstyle-suppressions.xml"/>
+    </module>
+
+    <!-- Checks for whitespace                               -->
+    <!-- See http://checkstyle.sf.net/config_whitespace.html -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <module name="TreeWalker">
+        <module name="OuterTypeFilename"/>
+        <module name="IllegalTokenText">
+            <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
+            <property name="format" value="\\u00(08|09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)"/>
+            <property name="message" value="Avoid using corresponding octal or Unicode escape."/>
+        </module>
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowEscapesForControlCharacters" value="true"/>
+            <property name="allowByTailComment" value="true"/>
+            <property name="allowNonPrintableEscapes" value="true"/>
+        </module>
+        <!-- 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"/>
+            <property name="tokens" value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
+        </module>
+        <module name="NeedBraces">
+            <property name="allowSingleLineStatement" value="true"/>
+	</module>
+        <module name="OneStatementPerLine"/>
+        <module name="ArrayTypeStyle"/>
+        <module name="FallThrough"/>
+        <module name="UpperEll"/>
+        <module name="ModifierOrder"/>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="DOT"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="COMMA"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+            <message key="name.invalidPattern"
+             value="Package name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ClassTypeParameterName">
+            <property name="format" value="([A-Z][a-zA-Z0-9]*$)"/>
+            <message key="name.invalidPattern"
+             value="Class type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MethodTypeParameterName">
+            <property name="format" value="([A-Z][a-zA-Z0-9]*)"/>
+            <message key="name.invalidPattern"
+             value="Method type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="NoFinalizer"/>
+        <module name="GenericWhitespace">
+            <message key="ws.followed"
+             value="GenericWhitespace ''{0}'' is followed by whitespace."/>
+             <message key="ws.preceded"
+             value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
+             <message key="ws.illegalFollow"
+             value="GenericWhitespace ''{0}'' should followed by whitespace."/>
+             <message key="ws.notPreceded"
+             value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <!-- TODO: 11/09/15 disabled - indentation is currently inconsistent -->
+        <!--
+        <module name="Indentation">
+            <property name="basicOffset" value="4"/>
+            <property name="braceAdjustment" value="0"/>
+            <property name="caseIndent" value="4"/>
+            <property name="throwsIndent" value="4"/>
+            <property name="lineWrappingIndentation" value="4"/>
+            <property name="arrayInitIndent" value="4"/>
+        </module>
+        -->
+        <!-- TODO: 11/09/15 disabled - order is currently wrong in many places -->
+        <!--
+        <module name="ImportOrder">
+            <property name="separated" value="true"/>
+            <property name="ordered" value="true"/>
+            <property name="groups" value="/^javax?\./,scala,*,org.apache.spark"/>
+        </module>
+        -->
+        <module name="MethodParamPad"/>
+        <module name="AnnotationLocation">
+            <property name="tokens" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF"/>
+        </module>
+        <module name="AnnotationLocation">
+            <property name="tokens" value="VARIABLE_DEF"/>
+            <property name="allowSamelineMultipleAnnotations" value="true"/>
+        </module>
+        <module name="MethodName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9_]*$"/>
+            <message key="name.invalidPattern"
+             value="Method name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected"/>
+        </module>
+        <module name="CommentsIndentation"/>
+    </module>
+</module>
diff --git a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorter.java b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorter.java
index c91e88f31b..c16cbce9a0 100644
--- a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorter.java
+++ b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorter.java
@@ -175,7 +175,7 @@ public final class UnsafeInMemorySorter {
       this.position = 0;
     }
 
-    public SortedIterator clone () {
+    public SortedIterator clone() {
       SortedIterator iter = new SortedIterator(numRecords);
       iter.position = position;
       iter.baseObject = baseObject;
diff --git a/core/src/test/java/org/apache/spark/unsafe/map/AbstractBytesToBytesMapSuite.java b/core/src/test/java/org/apache/spark/unsafe/map/AbstractBytesToBytesMapSuite.java
index d87a1d2a56..a5c583f9f2 100644
--- a/core/src/test/java/org/apache/spark/unsafe/map/AbstractBytesToBytesMapSuite.java
+++ b/core/src/test/java/org/apache/spark/unsafe/map/AbstractBytesToBytesMapSuite.java
@@ -356,8 +356,8 @@ public abstract class AbstractBytesToBytesMapSuite {
 
       final java.util.BitSet valuesSeen = new java.util.BitSet(NUM_ENTRIES);
       final Iterator<BytesToBytesMap.Location> iter = map.iterator();
-      final long key[] = new long[KEY_LENGTH / 8];
-      final long value[] = new long[VALUE_LENGTH / 8];
+      final long[] key = new long[KEY_LENGTH / 8];
+      final long[] value = new long[VALUE_LENGTH / 8];
       while (iter.hasNext()) {
         final BytesToBytesMap.Location loc = iter.next();
         Assert.assertTrue(loc.isDefined());
diff --git a/dev/lint-java b/dev/lint-java
new file mode 100755
index 0000000000..fe8ab83d56
--- /dev/null
+++ b/dev/lint-java
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+#
+# 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.
+#
+
+SCRIPT_DIR="$( cd "$( dirname "$0" )" && pwd )"
+SPARK_ROOT_DIR="$(dirname $SCRIPT_DIR)"
+
+ERRORS=$($SCRIPT_DIR/../build/mvn -Pkinesis-asl -Pyarn -Phive -Phive-thriftserver checkstyle:check | grep ERROR)
+
+if test ! -z "$ERRORS"; then
+    echo -e "Checkstyle checks failed at following occurrences:\n$ERRORS"
+    exit 1
+else
+    echo -e "Checkstyle checks passed."
+fi
diff --git a/dev/run-tests-jenkins.py b/dev/run-tests-jenkins.py
index 4f390ef1ea..7aecea25b2 100755
--- a/dev/run-tests-jenkins.py
+++ b/dev/run-tests-jenkins.py
@@ -119,6 +119,7 @@ def run_tests(tests_timeout):
         ERROR_CODES["BLOCK_GENERAL"]: 'some tests',
         ERROR_CODES["BLOCK_RAT"]: 'RAT tests',
         ERROR_CODES["BLOCK_SCALA_STYLE"]: 'Scala style tests',
+        ERROR_CODES["BLOCK_JAVA_STYLE"]: 'Java style tests',
         ERROR_CODES["BLOCK_PYTHON_STYLE"]: 'Python style tests',
         ERROR_CODES["BLOCK_R_STYLE"]: 'R style tests',
         ERROR_CODES["BLOCK_DOCUMENTATION"]: 'to generate documentation',
diff --git a/dev/run-tests.py b/dev/run-tests.py
index 9e1abb0697..e7e10f1d8c 100755
--- a/dev/run-tests.py
+++ b/dev/run-tests.py
@@ -198,6 +198,11 @@ def run_scala_style_checks():
     run_cmd([os.path.join(SPARK_HOME, "dev", "lint-scala")])
 
 
+def run_java_style_checks():
+    set_title_and_block("Running Java style checks", "BLOCK_JAVA_STYLE")
+    run_cmd([os.path.join(SPARK_HOME, "dev", "lint-java")])
+
+
 def run_python_style_checks():
     set_title_and_block("Running Python style checks", "BLOCK_PYTHON_STYLE")
     run_cmd([os.path.join(SPARK_HOME, "dev", "lint-python")])
@@ -522,6 +527,8 @@ def main():
     # style checks
     if not changed_files or any(f.endswith(".scala") for f in changed_files):
         run_scala_style_checks()
+    if not changed_files or any(f.endswith(".java") for f in changed_files):
+        run_java_style_checks()
     if not changed_files or any(f.endswith(".py") for f in changed_files):
         run_python_style_checks()
     if not changed_files or any(f.endswith(".R") for f in changed_files):
diff --git a/dev/sparktestsupport/__init__.py b/dev/sparktestsupport/__init__.py
index 8ab6d9e37c..0e8032d133 100644
--- a/dev/sparktestsupport/__init__.py
+++ b/dev/sparktestsupport/__init__.py
@@ -31,5 +31,6 @@ ERROR_CODES = {
     "BLOCK_SPARK_UNIT_TESTS": 18,
     "BLOCK_PYSPARK_UNIT_TESTS": 19,
     "BLOCK_SPARKR_UNIT_TESTS": 20,
+    "BLOCK_JAVA_STYLE": 21,
     "BLOCK_TIMEOUT": 124
 }
diff --git a/examples/src/main/java/org/apache/spark/examples/ml/JavaSimpleParamsExample.java b/examples/src/main/java/org/apache/spark/examples/ml/JavaSimpleParamsExample.java
index 94beeced3d..ea83e8fef9 100644
--- a/examples/src/main/java/org/apache/spark/examples/ml/JavaSimpleParamsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/ml/JavaSimpleParamsExample.java
@@ -77,7 +77,7 @@ public class JavaSimpleParamsExample {
     ParamMap paramMap = new ParamMap();
     paramMap.put(lr.maxIter().w(20)); // Specify 1 Param.
     paramMap.put(lr.maxIter(), 30); // This overwrites the original maxIter.
-    double thresholds[] = {0.45, 0.55};
+    double[] thresholds = {0.45, 0.55};
     paramMap.put(lr.regParam().w(0.1), lr.thresholds().w(thresholds)); // Specify multiple Params.
 
     // One can also combine ParamMaps.
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaLDAExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaLDAExample.java
index fd53c81cc4..de8e739ac9 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaLDAExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaLDAExample.java
@@ -41,8 +41,9 @@ public class JavaLDAExample {
           public Vector call(String s) {
             String[] sarray = s.trim().split(" ");
             double[] values = new double[sarray.length];
-            for (int i = 0; i < sarray.length; i++)
+            for (int i = 0; i < sarray.length; i++) {
               values[i] = Double.parseDouble(sarray[i]);
+            }
             return Vectors.dense(values);
           }
         }
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
index b54e1ea3f2..5ba01e0d08 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
@@ -57,12 +57,12 @@ public class JavaMultiLabelClassificationMetricsExample {
 
     // Stats by labels
     for (int i = 0; i < metrics.labels().length - 1; i++) {
-      System.out.format("Class %1.1f precision = %f\n", metrics.labels()[i], metrics.precision
-        (metrics.labels()[i]));
-      System.out.format("Class %1.1f recall = %f\n", metrics.labels()[i], metrics.recall(metrics
-        .labels()[i]));
-      System.out.format("Class %1.1f F1 score = %f\n", metrics.labels()[i], metrics.f1Measure
-        (metrics.labels()[i]));
+      System.out.format("Class %1.1f precision = %f\n", metrics.labels()[i], metrics.precision(
+        metrics.labels()[i]));
+      System.out.format("Class %1.1f recall = %f\n", metrics.labels()[i], metrics.recall(
+        metrics.labels()[i]));
+      System.out.format("Class %1.1f F1 score = %f\n", metrics.labels()[i], metrics.f1Measure(
+        metrics.labels()[i]));
     }
 
     // Micro stats
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMulticlassClassificationMetricsExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMulticlassClassificationMetricsExample.java
index 21f628fb51..5247c9c748 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMulticlassClassificationMetricsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMulticlassClassificationMetricsExample.java
@@ -74,12 +74,12 @@ public class JavaMulticlassClassificationMetricsExample {
 
     // Stats by labels
     for (int i = 0; i < metrics.labels().length; i++) {
-      System.out.format("Class %f precision = %f\n", metrics.labels()[i],metrics.precision
-        (metrics.labels()[i]));
-      System.out.format("Class %f recall = %f\n", metrics.labels()[i], metrics.recall(metrics
-        .labels()[i]));
-      System.out.format("Class %f F1 score = %f\n", metrics.labels()[i], metrics.fMeasure
-        (metrics.labels()[i]));
+      System.out.format("Class %f precision = %f\n", metrics.labels()[i],metrics.precision(
+        metrics.labels()[i]));
+      System.out.format("Class %f recall = %f\n", metrics.labels()[i], metrics.recall(
+        metrics.labels()[i]));
+      System.out.format("Class %f F1 score = %f\n", metrics.labels()[i], metrics.fMeasure(
+        metrics.labels()[i]));
     }
 
     //Weighted stats
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRankingMetricsExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRankingMetricsExample.java
index 7c4c97e746..47ab3fc358 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRankingMetricsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRankingMetricsExample.java
@@ -120,8 +120,8 @@ public class JavaRankingMetricsExample {
         }
       }
     );
-    JavaRDD<Tuple2<List<Integer>, List<Integer>>> relevantDocs = userMoviesList.join
-      (userRecommendedList).values();
+    JavaRDD<Tuple2<List<Integer>, List<Integer>>> relevantDocs = userMoviesList.join(
+      userRecommendedList).values();
 
     // Instantiate the metrics object
     RankingMetrics metrics = RankingMetrics.of(relevantDocs);
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRecommendationExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRecommendationExample.java
index 1065fde953..c179e7578c 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRecommendationExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRecommendationExample.java
@@ -29,7 +29,7 @@ import org.apache.spark.SparkConf;
 // $example off$
 
 public class JavaRecommendationExample {
-  public static void main(String args[]) {
+  public static void main(String[] args) {
     // $example on$
     SparkConf conf = new SparkConf().setAppName("Java Collaborative Filtering Example");
     JavaSparkContext jsc = new JavaSparkContext(conf);
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRegressionMetricsExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRegressionMetricsExample.java
index d2efc6bf97..4e89dd0c37 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaRegressionMetricsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaRegressionMetricsExample.java
@@ -43,8 +43,9 @@ public class JavaRegressionMetricsExample {
         public LabeledPoint call(String line) {
           String[] parts = line.split(" ");
           double[] v = new double[parts.length - 1];
-          for (int i = 1; i < parts.length - 1; i++)
+          for (int i = 1; i < parts.length - 1; i++) {
             v[i - 1] = Double.parseDouble(parts[i].split(":")[1]);
+          }
           return new LabeledPoint(Double.parseDouble(parts[0]), Vectors.dense(v));
         }
       }
diff --git a/examples/src/main/java/org/apache/spark/examples/streaming/JavaSqlNetworkWordCount.java b/examples/src/main/java/org/apache/spark/examples/streaming/JavaSqlNetworkWordCount.java
index 46562ddbbc..3515d7be45 100644
--- a/examples/src/main/java/org/apache/spark/examples/streaming/JavaSqlNetworkWordCount.java
+++ b/examples/src/main/java/org/apache/spark/examples/streaming/JavaSqlNetworkWordCount.java
@@ -112,8 +112,8 @@ public final class JavaSqlNetworkWordCount {
 
 /** Lazily instantiated singleton instance of SQLContext */
 class JavaSQLContextSingleton {
-  static private transient SQLContext instance = null;
-  static public SQLContext getInstance(SparkContext sparkContext) {
+  private static transient SQLContext instance = null;
+  public static SQLContext getInstance(SparkContext sparkContext) {
     if (instance == null) {
       instance = new SQLContext(sparkContext);
     }
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;
diff --git a/network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockResolver.java b/network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockResolver.java
index 0d4dd6afac..e5cb68c8a4 100644
--- a/network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockResolver.java
+++ b/network/shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalShuffleBlockResolver.java
@@ -419,7 +419,7 @@ public class ExternalShuffleBlockResolver {
 
   public static class StoreVersion {
 
-    final static byte[] KEY = "StoreVersion".getBytes(Charsets.UTF_8);
+    static final byte[] KEY = "StoreVersion".getBytes(Charsets.UTF_8);
 
     public final int major;
     public final int minor;
diff --git a/network/shuffle/src/test/java/org/apache/spark/network/sasl/SaslIntegrationSuite.java b/network/shuffle/src/test/java/org/apache/spark/network/sasl/SaslIntegrationSuite.java
index 19c870aebb..f573d962fe 100644
--- a/network/shuffle/src/test/java/org/apache/spark/network/sasl/SaslIntegrationSuite.java
+++ b/network/shuffle/src/test/java/org/apache/spark/network/sasl/SaslIntegrationSuite.java
@@ -61,7 +61,7 @@ public class SaslIntegrationSuite {
 
   // Use a long timeout to account for slow / overloaded build machines. In the normal case,
   // tests should finish way before the timeout expires.
-  private final static long TIMEOUT_MS = 10_000;
+  private static final long TIMEOUT_MS = 10_000;
 
   static TransportServer server;
   static TransportConf conf;
diff --git a/pom.xml b/pom.xml
index 234fd5dea1..16e656d119 100644
--- a/pom.xml
+++ b/pom.xml
@@ -2256,6 +2256,30 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-checkstyle-plugin</artifactId>
+        <version>2.17</version>
+        <configuration>
+          <verbose>false</verbose>
+          <failOnViolation>false</failOnViolation>
+          <includeTestSourceDirectory>true</includeTestSourceDirectory>
+          <failOnWarning>false</failOnWarning>
+          <sourceDirectory>${basedir}/src/main/java</sourceDirectory>
+          <testSourceDirectory>${basedir}/src/test/java</testSourceDirectory>
+          <configLocation>checkstyle.xml</configLocation>
+          <outputFile>${basedir}/target/checkstyle-output.xml</outputFile>
+          <inputEncoding>${project.build.sourceEncoding}</inputEncoding>
+          <outputEncoding>${project.reporting.outputEncoding}</outputEncoding>
+        </configuration>
+        <executions>
+          <execution>
+            <goals>
+              <goal>check</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
 
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java b/sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java
index 3986d6e18f..352002b349 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java
@@ -51,7 +51,7 @@ final class UnsafeExternalRowSorter {
   private final PrefixComputer prefixComputer;
   private final UnsafeExternalSorter sorter;
 
-  public static abstract class PrefixComputer {
+  public abstract static class PrefixComputer {
     abstract long computePrefix(InternalRow row);
   }
 
diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/types/SQLUserDefinedType.java b/sql/catalyst/src/main/java/org/apache/spark/sql/types/SQLUserDefinedType.java
index df64a878b6..1e4e5ede8c 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/types/SQLUserDefinedType.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/types/SQLUserDefinedType.java
@@ -41,5 +41,5 @@ public @interface SQLUserDefinedType {
    * Returns an instance of the UserDefinedType which can serialize and deserialize the user
    * class to and from Catalyst built-in types.
    */
-  Class<? extends UserDefinedType<?> > udt();
+  Class<? extends UserDefinedType<?>> udt();
 }
diff --git a/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java b/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java
index 2ed30c1f5a..842dcb8c93 100644
--- a/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java
+++ b/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java
@@ -195,7 +195,7 @@ public abstract class SpecificParquetRecordReaderBase<T> extends RecordReader<Vo
    * Creates a reader for definition and repetition levels, returning an optimized one if
    * the levels are not needed.
    */
-  static protected IntIterator createRLEIterator(int maxLevel, BytesInput bytes,
+  protected static IntIterator createRLEIterator(int maxLevel, BytesInput bytes,
                                               ColumnDescriptor descriptor) throws IOException {
     try {
       if (maxLevel == 0) return new NullIntIterator();
diff --git a/sql/hive/src/test/java/org/apache/spark/sql/hive/test/Complex.java b/sql/hive/src/test/java/org/apache/spark/sql/hive/test/Complex.java
index e010112bb9..4ef1f276d1 100644
--- a/sql/hive/src/test/java/org/apache/spark/sql/hive/test/Complex.java
+++ b/sql/hive/src/test/java/org/apache/spark/sql/hive/test/Complex.java
@@ -489,6 +489,7 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       }
       break;
 
+    default:
     }
   }
 
@@ -512,6 +513,7 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
     case M_STRING_STRING:
       return getMStringString();
 
+    default:
     }
     throw new IllegalStateException();
   }
@@ -535,75 +537,91 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       return isSetLintString();
     case M_STRING_STRING:
       return isSetMStringString();
+    default:
     }
     throw new IllegalStateException();
   }
 
   @Override
   public boolean equals(Object that) {
-    if (that == null)
+    if (that == null) {
       return false;
-    if (that instanceof Complex)
+    }
+    if (that instanceof Complex) {
       return this.equals((Complex)that);
+    }
     return false;
   }
 
   public boolean equals(Complex that) {
-    if (that == null)
+    if (that == null) {
       return false;
+    }
 
     boolean this_present_aint = true;
     boolean that_present_aint = true;
     if (this_present_aint || that_present_aint) {
-      if (!(this_present_aint && that_present_aint))
+      if (!(this_present_aint && that_present_aint)) {
         return false;
-      if (this.aint != that.aint)
+      }
+      if (this.aint != that.aint) {
         return false;
+      }
     }
 
     boolean this_present_aString = true && this.isSetAString();
     boolean that_present_aString = true && that.isSetAString();
     if (this_present_aString || that_present_aString) {
-      if (!(this_present_aString && that_present_aString))
+      if (!(this_present_aString && that_present_aString)) {
         return false;
-      if (!this.aString.equals(that.aString))
+      }
+      if (!this.aString.equals(that.aString)) {
         return false;
+      }
     }
 
     boolean this_present_lint = true && this.isSetLint();
     boolean that_present_lint = true && that.isSetLint();
     if (this_present_lint || that_present_lint) {
-      if (!(this_present_lint && that_present_lint))
+      if (!(this_present_lint && that_present_lint)) {
         return false;
-      if (!this.lint.equals(that.lint))
+      }
+      if (!this.lint.equals(that.lint)) {
         return false;
+      }
     }
 
     boolean this_present_lString = true && this.isSetLString();
     boolean that_present_lString = true && that.isSetLString();
     if (this_present_lString || that_present_lString) {
-      if (!(this_present_lString && that_present_lString))
+      if (!(this_present_lString && that_present_lString)) {
         return false;
-      if (!this.lString.equals(that.lString))
+      }
+      if (!this.lString.equals(that.lString)) {
         return false;
+      }
     }
 
     boolean this_present_lintString = true && this.isSetLintString();
     boolean that_present_lintString = true && that.isSetLintString();
     if (this_present_lintString || that_present_lintString) {
-      if (!(this_present_lintString && that_present_lintString))
+      if (!(this_present_lintString && that_present_lintString)) {
         return false;
-      if (!this.lintString.equals(that.lintString))
+      }
+      if (!this.lintString.equals(that.lintString)) {
         return false;
+      }
     }
 
     boolean this_present_mStringString = true && this.isSetMStringString();
     boolean that_present_mStringString = true && that.isSetMStringString();
     if (this_present_mStringString || that_present_mStringString) {
-      if (!(this_present_mStringString && that_present_mStringString))
+      if (!(this_present_mStringString && that_present_mStringString)) {
         return false;
-      if (!this.mStringString.equals(that.mStringString))
+      }
+      if (!this.mStringString.equals(that.mStringString)) {
         return false;
+      }
     }
 
     return true;
@@ -615,33 +633,39 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
 
     boolean present_aint = true;
     builder.append(present_aint);
-    if (present_aint)
+    if (present_aint) {
       builder.append(aint);
+    }
 
     boolean present_aString = true && (isSetAString());
     builder.append(present_aString);
-    if (present_aString)
+    if (present_aString) {
       builder.append(aString);
+    }
 
     boolean present_lint = true && (isSetLint());
     builder.append(present_lint);
-    if (present_lint)
+    if (present_lint) {
       builder.append(lint);
+    }
 
     boolean present_lString = true && (isSetLString());
     builder.append(present_lString);
-    if (present_lString)
+    if (present_lString) {
       builder.append(lString);
+    }
 
     boolean present_lintString = true && (isSetLintString());
     builder.append(present_lintString);
-    if (present_lintString)
+    if (present_lintString) {
       builder.append(lintString);
+    }
 
     boolean present_mStringString = true && (isSetMStringString());
     builder.append(present_mStringString);
-    if (present_mStringString)
+    if (present_mStringString) {
       builder.append(mStringString);
+    }
 
     return builder.toHashCode();
   }
@@ -737,7 +761,9 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
     sb.append("aint:");
     sb.append(this.aint);
     first = false;
-    if (!first) sb.append(", ");
+    if (!first) {
+      sb.append(", ");
+    }
     sb.append("aString:");
     if (this.aString == null) {
       sb.append("null");
@@ -745,7 +771,9 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       sb.append(this.aString);
     }
     first = false;
-    if (!first) sb.append(", ");
+    if (!first) {
+      sb.append(", ");
+    }
     sb.append("lint:");
     if (this.lint == null) {
       sb.append("null");
@@ -753,7 +781,9 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       sb.append(this.lint);
     }
     first = false;
-    if (!first) sb.append(", ");
+    if (!first) {
+      sb.append(", ");
+    }
     sb.append("lString:");
     if (this.lString == null) {
       sb.append("null");
@@ -761,7 +791,9 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       sb.append(this.lString);
     }
     first = false;
-    if (!first) sb.append(", ");
+    if (!first) {
+      sb.append(", ");
+    }
     sb.append("lintString:");
     if (this.lintString == null) {
       sb.append("null");
@@ -769,7 +801,9 @@ public class Complex implements org.apache.thrift.TBase<Complex, Complex._Fields
       sb.append(this.lintString);
     }
     first = false;
-    if (!first) sb.append(", ");
+    if (!first) {
+      sb.append(", ");
+    }
     sb.append("mStringString:");
     if (this.mStringString == null) {
       sb.append("null");
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))
diff --git a/tags/src/main/java/org/apache/spark/tags/ExtendedHiveTest.java b/tags/src/main/java/org/apache/spark/tags/ExtendedHiveTest.java
index 1b0c416b0f..83279e5e93 100644
--- a/tags/src/main/java/org/apache/spark/tags/ExtendedHiveTest.java
+++ b/tags/src/main/java/org/apache/spark/tags/ExtendedHiveTest.java
@@ -18,6 +18,7 @@
 package org.apache.spark.tags;
 
 import java.lang.annotation.*;
+
 import org.scalatest.TagAnnotation;
 
 @TagAnnotation
diff --git a/tags/src/main/java/org/apache/spark/tags/ExtendedYarnTest.java b/tags/src/main/java/org/apache/spark/tags/ExtendedYarnTest.java
index 2a631bfc88..108300168e 100644
--- a/tags/src/main/java/org/apache/spark/tags/ExtendedYarnTest.java
+++ b/tags/src/main/java/org/apache/spark/tags/ExtendedYarnTest.java
@@ -18,6 +18,7 @@
 package org.apache.spark.tags;
 
 import java.lang.annotation.*;
+
 import org.scalatest.TagAnnotation;
 
 @TagAnnotation
diff --git a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
index 4bd3fd7772..5b61386808 100644
--- a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
+++ b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
@@ -900,9 +900,9 @@ public final class UTF8String implements Comparable<UTF8String>, Externalizable,
       m = swap;
     }
 
-    int p[] = new int[n + 1];
-    int d[] = new int[n + 1];
-    int swap[];
+    int[] p = new int[n + 1];
+    int[] d = new int[n + 1];
+    int[] swap;
 
     int i, i_bytes, j, j_bytes, num_bytes_j, cost;
 
@@ -965,7 +965,7 @@ public final class UTF8String implements Comparable<UTF8String>, Externalizable,
       // first character must be a letter
       return this;
     }
-    byte sx[] = {'0', '0', '0', '0'};
+    byte[] sx = {'0', '0', '0', '0'};
     sx[0] = b;
     int sxi = 1;
     int idx = b - 'A';