[SPARK-9534] [BUILD] Enable javac lint for scalac parity; fix a lot of build warnings, 1.5.0 edition

Enable most javac lint warnings; fix a lot of build warnings. In a few cases, touch up surrounding code in the process.

I'll explain several of the changes inline in comments.

Author: Sean Owen <sowen@cloudera.com>

Closes #7862 from srowen/SPARK-9534 and squashes the following commits:

ea51618 [Sean Owen] Enable most javac lint warnings; fix a lot of build warnings. In a few cases, touch up surrounding code in the process.

4 files changed, 28 insertions, 16 deletions

diff --git a/core/src/main/java/org/apache/spark/api/java/JavaSparkContextVarargsWorkaround.java b/core/src/main/java/org/apache/spark/api/java/JavaSparkContextVarargsWorkaround.java
index 2090efd3b9..d4c42b38ac 100644
--- a/core/src/main/java/org/apache/spark/api/java/JavaSparkContextVarargsWorkaround.java
+++ b/core/src/main/java/org/apache/spark/api/java/JavaSparkContextVarargsWorkaround.java
@@ -23,11 +23,13 @@ import java.util.List;
 // See
 // http://scala-programming-language.1934581.n4.nabble.com/Workaround-for-implementing-java-varargs-in-2-7-2-final-tp1944767p1944772.html
 abstract class JavaSparkContextVarargsWorkaround {
-  public <T> JavaRDD<T> union(JavaRDD<T>... rdds) {
+
+  @SafeVarargs
+  public final <T> JavaRDD<T> union(JavaRDD<T>... rdds) {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    ArrayList<JavaRDD<T>> rest = new ArrayList<JavaRDD<T>>(rdds.length - 1);
+    List<JavaRDD<T>> rest = new ArrayList<>(rdds.length - 1);
     for (int i = 1; i < rdds.length; i++) {
       rest.add(rdds[i]);
     }
@@ -38,18 +40,19 @@ abstract class JavaSparkContextVarargsWorkaround {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    ArrayList<JavaDoubleRDD> rest = new ArrayList<JavaDoubleRDD>(rdds.length - 1);
+    List<JavaDoubleRDD> rest = new ArrayList<>(rdds.length - 1);
     for (int i = 1; i < rdds.length; i++) {
       rest.add(rdds[i]);
     }
     return union(rdds[0], rest);
   }
 
-  public <K, V> JavaPairRDD<K, V> union(JavaPairRDD<K, V>... rdds) {
+  @SafeVarargs
+  public final <K, V> JavaPairRDD<K, V> union(JavaPairRDD<K, V>... rdds) {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    ArrayList<JavaPairRDD<K, V>> rest = new ArrayList<JavaPairRDD<K, V>>(rdds.length - 1);
+    List<JavaPairRDD<K, V>> rest = new ArrayList<>(rdds.length - 1);
     for (int i = 1; i < rdds.length; i++) {
       rest.add(rdds[i]);
     }
@@ -57,7 +60,7 @@ abstract class JavaSparkContextVarargsWorkaround {
   }
 
   // These methods take separate "first" and "rest" elements to avoid having the same type erasure
-  abstract public <T> JavaRDD<T> union(JavaRDD<T> first, List<JavaRDD<T>> rest);
-  abstract public JavaDoubleRDD union(JavaDoubleRDD first, List<JavaDoubleRDD> rest);
-  abstract public <K, V> JavaPairRDD<K, V> union(JavaPairRDD<K, V> first, List<JavaPairRDD<K, V>> rest);
+  public abstract <T> JavaRDD<T> union(JavaRDD<T> first, List<JavaRDD<T>> rest);
+  public abstract JavaDoubleRDD union(JavaDoubleRDD first, List<JavaDoubleRDD> rest);
+  public abstract <K, V> JavaPairRDD<K, V> union(JavaPairRDD<K, V> first, List<JavaPairRDD<K, V>> rest);
 }
diff --git a/core/src/main/scala/org/apache/spark/storage/TachyonBlockManager.scala b/core/src/main/scala/org/apache/spark/storage/TachyonBlockManager.scala
index b53c86e89a..ebad5bc5ab 100644
--- a/core/src/main/scala/org/apache/spark/storage/TachyonBlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/storage/TachyonBlockManager.scala
@@ -27,9 +27,10 @@ import scala.util.control.NonFatal
 import com.google.common.io.ByteStreams
 
 import tachyon.client.{ReadType, WriteType, TachyonFS, TachyonFile}
+import tachyon.conf.TachyonConf
 import tachyon.TachyonURI
 
-import org.apache.spark.{SparkException, SparkConf, Logging}
+import org.apache.spark.Logging
 import org.apache.spark.executor.ExecutorExitCode
 import org.apache.spark.util.Utils
 
@@ -60,7 +61,11 @@ private[spark] class TachyonBlockManager() extends ExternalBlockManager with Log
 
     rootDirs = s"$storeDir/$appFolderName/$executorId"
     master = blockManager.conf.get(ExternalBlockStore.MASTER_URL, "tachyon://localhost:19998")
-    client = if (master != null && master != "") TachyonFS.get(new TachyonURI(master)) else null
+    client = if (master != null && master != "") {
+      TachyonFS.get(new TachyonURI(master), new TachyonConf())
+    } else {
+      null
+    }
     // original implementation call System.exit, we change it to run without extblkstore support
     if (client == null) {
       logError("Failed to connect to the Tachyon as the master address is not configured")
diff --git a/core/src/test/scala/org/apache/spark/deploy/master/PersistenceEngineSuite.scala b/core/src/test/scala/org/apache/spark/deploy/master/PersistenceEngineSuite.scala
index 11e87bd1dd..34775577de 100644
--- a/core/src/test/scala/org/apache/spark/deploy/master/PersistenceEngineSuite.scala
+++ b/core/src/test/scala/org/apache/spark/deploy/master/PersistenceEngineSuite.scala
@@ -73,11 +73,11 @@ class PersistenceEngineSuite extends SparkFunSuite {
     assert(persistenceEngine.read[String]("test_").isEmpty)
 
     // Test deserializing objects that contain RpcEndpointRef
-    val rpcEnv = RpcEnv.create("test", "localhost", 12345, conf, new SecurityManager(conf))
+    val testRpcEnv = RpcEnv.create("test", "localhost", 12345, conf, new SecurityManager(conf))
     try {
       // Create a real endpoint so that we can test RpcEndpointRef deserialization
-      val workerEndpoint = rpcEnv.setupEndpoint("worker", new RpcEndpoint {
-        override val rpcEnv: RpcEnv = rpcEnv
+      val workerEndpoint = testRpcEnv.setupEndpoint("worker", new RpcEndpoint {
+        override val rpcEnv: RpcEnv = testRpcEnv
       })
 
       val workerToPersist = new WorkerInfo(
@@ -93,7 +93,8 @@ class PersistenceEngineSuite extends SparkFunSuite {
 
       persistenceEngine.addWorker(workerToPersist)
 
-      val (storedApps, storedDrivers, storedWorkers) = persistenceEngine.readPersistedData(rpcEnv)
+      val (storedApps, storedDrivers, storedWorkers) =
+        persistenceEngine.readPersistedData(testRpcEnv)
 
       assert(storedApps.isEmpty)
       assert(storedDrivers.isEmpty)
@@ -110,8 +111,8 @@ class PersistenceEngineSuite extends SparkFunSuite {
       assert(workerToPersist.webUiPort === recoveryWorkerInfo.webUiPort)
       assert(workerToPersist.publicAddress === recoveryWorkerInfo.publicAddress)
     } finally {
-      rpcEnv.shutdown()
-      rpcEnv.awaitTermination()
+      testRpcEnv.shutdown()
+      testRpcEnv.awaitTermination()
     }
   }
 
diff --git a/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerUtilsSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerUtilsSuite.scala
index b354914b6f..2eb43b7313 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerUtilsSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerUtilsSuite.scala
@@ -17,10 +17,13 @@
 
 package org.apache.spark.scheduler.cluster.mesos
 
+import scala.language.reflectiveCalls
+
 import org.apache.mesos.Protos.Value
 import org.mockito.Mockito._
 import org.scalatest._
 import org.scalatest.mock.MockitoSugar
+
 import org.apache.spark.{SparkConf, SparkContext, SparkFunSuite}
 
 class MesosSchedulerUtilsSuite extends SparkFunSuite with Matchers with MockitoSugar {