[SPARK-6428] Turn on explicit type checking for public methods.

This builds on my earlier pull requests and turns on the explicit type checking in scalastyle.

Author: Reynold Xin <rxin@databricks.com>

Closes #5342 from rxin/SPARK-6428 and squashes the following commits:

7b531ab [Reynold Xin] import ordering
2d9a8a5 [Reynold Xin] jl
e668b1c [Reynold Xin] override
9b9e119 [Reynold Xin] Parenthesis.
82e0cf5 [Reynold Xin] [SPARK-6428] Turn on explicit type checking for public methods.

2 files changed, 36 insertions, 32 deletions

diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMaster.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMaster.scala
index 3d18690cd9..455554eea0 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMaster.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMaster.scala
@@ -162,7 +162,7 @@ private[spark] class ApplicationMaster(
    * status to SUCCEEDED in cluster mode to handle if the user calls System.exit
    * from the application code.
    */
-  final def getDefaultFinalStatus() = {
+  final def getDefaultFinalStatus(): FinalApplicationStatus = {
     if (isClusterMode) {
       FinalApplicationStatus.SUCCEEDED
     } else {
@@ -175,31 +175,35 @@ private[spark] class ApplicationMaster(
    * This means the ResourceManager will not retry the application attempt on your behalf if
    * a failure occurred.
    */
-  final def unregister(status: FinalApplicationStatus, diagnostics: String = null) = synchronized {
-    if (!unregistered) {
-      logInfo(s"Unregistering ApplicationMaster with $status" +
-        Option(diagnostics).map(msg => s" (diag message: $msg)").getOrElse(""))
-      unregistered = true
-      client.unregister(status, Option(diagnostics).getOrElse(""))
+  final def unregister(status: FinalApplicationStatus, diagnostics: String = null): Unit = {
+    synchronized {
+      if (!unregistered) {
+        logInfo(s"Unregistering ApplicationMaster with $status" +
+          Option(diagnostics).map(msg => s" (diag message: $msg)").getOrElse(""))
+        unregistered = true
+        client.unregister(status, Option(diagnostics).getOrElse(""))
+      }
     }
   }
 
-  final def finish(status: FinalApplicationStatus, code: Int, msg: String = null) = synchronized {
-    if (!finished) {
-      val inShutdown = Utils.inShutdown()
-      logInfo(s"Final app status: ${status}, exitCode: ${code}" +
-        Option(msg).map(msg => s", (reason: $msg)").getOrElse(""))
-      exitCode = code
-      finalStatus = status
-      finalMsg = msg
-      finished = true
-      if (!inShutdown && Thread.currentThread() != reporterThread && reporterThread != null) {
-        logDebug("shutting down reporter thread")
-        reporterThread.interrupt()
-      }
-      if (!inShutdown && Thread.currentThread() != userClassThread && userClassThread != null) {
-        logDebug("shutting down user thread")
-        userClassThread.interrupt()
+  final def finish(status: FinalApplicationStatus, code: Int, msg: String = null): Unit = {
+    synchronized {
+      if (!finished) {
+        val inShutdown = Utils.inShutdown()
+        logInfo(s"Final app status: $status, exitCode: $code" +
+          Option(msg).map(msg => s", (reason: $msg)").getOrElse(""))
+        exitCode = code
+        finalStatus = status
+        finalMsg = msg
+        finished = true
+        if (!inShutdown && Thread.currentThread() != reporterThread && reporterThread != null) {
+          logDebug("shutting down reporter thread")
+          reporterThread.interrupt()
+        }
+        if (!inShutdown && Thread.currentThread() != userClassThread && userClassThread != null) {
+          logDebug("shutting down user thread")
+          userClassThread.interrupt()
+        }
       }
     }
   }
@@ -506,7 +510,7 @@ private[spark] class ApplicationMaster(
   private class AMActor(driverUrl: String, isClusterMode: Boolean) extends Actor {
     var driver: ActorSelection = _
 
-    override def preStart() = {
+    override def preStart(): Unit = {
       logInfo("Listen to driver: " + driverUrl)
       driver = context.actorSelection(driverUrl)
       // Send a hello message to establish the connection, after which
@@ -520,7 +524,7 @@ private[spark] class ApplicationMaster(
       }
     }
 
-    override def receive = {
+    override def receive: PartialFunction[Any, Unit] = {
       case x: DisassociatedEvent =>
         logInfo(s"Driver terminated or disconnected! Shutting down. $x")
         // In cluster mode, do not rely on the disassociated event to exit
@@ -567,7 +571,7 @@ object ApplicationMaster extends Logging {
 
   private var master: ApplicationMaster = _
 
-  def main(args: Array[String]) = {
+  def main(args: Array[String]): Unit = {
     SignalLogger.register(log)
     val amArgs = new ApplicationMasterArguments(args)
     SparkHadoopUtil.get.runAsSparkUser { () =>
@@ -576,11 +580,11 @@ object ApplicationMaster extends Logging {
     }
   }
 
-  private[spark] def sparkContextInitialized(sc: SparkContext) = {
+  private[spark] def sparkContextInitialized(sc: SparkContext): Unit = {
     master.sparkContextInitialized(sc)
   }
 
-  private[spark] def sparkContextStopped(sc: SparkContext) = {
+  private[spark] def sparkContextStopped(sc: SparkContext): Boolean = {
     master.sparkContextStopped(sc)
   }
 
@@ -592,7 +596,7 @@ object ApplicationMaster extends Logging {
  */
 object ExecutorLauncher {
 
-  def main(args: Array[String]) = {
+  def main(args: Array[String]): Unit = {
     ApplicationMaster.main(args)
   }
 
diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
index c1d3f7320f..1ce10d906a 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
@@ -59,15 +59,15 @@ class ExecutorRunnable(
   val yarnConf: YarnConfiguration = new YarnConfiguration(conf)
   lazy val env = prepareEnvironment(container)
 
-  def run = {
+  override def run(): Unit = {
     logInfo("Starting Executor Container")
     nmClient = NMClient.createNMClient()
     nmClient.init(yarnConf)
     nmClient.start()
-    startContainer
+    startContainer()
   }
 
-  def startContainer = {
+  def startContainer(): java.util.Map[String, ByteBuffer] = {
     logInfo("Setting up ContainerLaunchContext")
 
     val ctx = Records.newRecord(classOf[ContainerLaunchContext])