[SPARK-6428] Added explicit types for all public methods in core.

Author: Reynold Xin <[email protected]>

Closes apache#5125 from rxin/core-explicit-type and squashes the following commits:

f471415 [Reynold Xin] Revert style checker changes.
81b66e4 [Reynold Xin] Code review feedback.
a7533e3 [Reynold Xin] Mima excludes.
1d795f5 [Reynold Xin] [SPARK-6428] Added explicit types for all public methods in core.

core/src/main/scala/org/apache/spark/Accumulators.scala

@@ -18,8 +18,6 @@
 package org.apache.spark
 
 import java.io.{ObjectInputStream, Serializable}
-import java.util.concurrent.atomic.AtomicLong
-import java.lang.ThreadLocal
 
 import scala.collection.generic.Growable
 import scala.collection.mutable.Map
@@ -109,7 +107,7 @@ class Accumulable[R, T] (
    * The typical use of this method is to directly mutate the local value, eg., to add
    * an element to a Set.
    */
-  def localValue = value_
+  def localValue: R = value_
 
   /**
    * Set the accumulator's value; only allowed on master.
@@ -137,7 +135,7 @@ class Accumulable[R, T] (
     Accumulators.register(this, false)
   }
 
-  override def toString = if (value_ == null) "null" else value_.toString
+  override def toString: String = if (value_ == null) "null" else value_.toString
 }
 
 /**
@@ -257,22 +255,22 @@ object AccumulatorParam {
 
   implicit object DoubleAccumulatorParam extends AccumulatorParam[Double] {
     def addInPlace(t1: Double, t2: Double): Double = t1 + t2
-    def zero(initialValue: Double) = 0.0
+    def zero(initialValue: Double): Double = 0.0
   }
 
   implicit object IntAccumulatorParam extends AccumulatorParam[Int] {
     def addInPlace(t1: Int, t2: Int): Int = t1 + t2
-    def zero(initialValue: Int) = 0
+    def zero(initialValue: Int): Int = 0
   }
 
   implicit object LongAccumulatorParam extends AccumulatorParam[Long] {
-    def addInPlace(t1: Long, t2: Long) = t1 + t2
-    def zero(initialValue: Long) = 0L
+    def addInPlace(t1: Long, t2: Long): Long = t1 + t2
+    def zero(initialValue: Long): Long = 0L
   }
 
   implicit object FloatAccumulatorParam extends AccumulatorParam[Float] {
-    def addInPlace(t1: Float, t2: Float) = t1 + t2
-    def zero(initialValue: Float) = 0f
+    def addInPlace(t1: Float, t2: Float): Float = t1 + t2
+    def zero(initialValue: Float): Float = 0f
   }
 
   // TODO: Add AccumulatorParams for other types, e.g. lists and strings
@@ -351,6 +349,7 @@ private[spark] object Accumulators extends Logging {
     }
   }
 
-  def stringifyPartialValue(partialValue: Any) = "%s".format(partialValue)
-  def stringifyValue(value: Any) = "%s".format(value)
+  def stringifyPartialValue(partialValue: Any): String = "%s".format(partialValue)
+
+  def stringifyValue(value: Any): String = "%s".format(value)
 }

core/src/main/scala/org/apache/spark/Dependency.scala

@@ -74,7 +74,7 @@ class ShuffleDependency[K, V, C](
     val mapSideCombine: Boolean = false)
   extends Dependency[Product2[K, V]] {
 
-  override def rdd = _rdd.asInstanceOf[RDD[Product2[K, V]]]
+  override def rdd: RDD[Product2[K, V]] = _rdd.asInstanceOf[RDD[Product2[K, V]]]
 
   val shuffleId: Int = _rdd.context.newShuffleId()
 
@@ -91,7 +91,7 @@ class ShuffleDependency[K, V, C](
  */
 @DeveloperApi
 class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
-  override def getParents(partitionId: Int) = List(partitionId)
+  override def getParents(partitionId: Int): List[Int] = List(partitionId)
 }
 
 
@@ -107,7 +107,7 @@ class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
 class RangeDependency[T](rdd: RDD[T], inStart: Int, outStart: Int, length: Int)
   extends NarrowDependency[T](rdd) {
 
-  override def getParents(partitionId: Int) = {
+  override def getParents(partitionId: Int): List[Int] = {
     if (partitionId >= outStart && partitionId < outStart + length) {
       List(partitionId - outStart + inStart)
     } else {

core/src/main/scala/org/apache/spark/FutureAction.scala

@@ -168,7 +168,7 @@ class SimpleFutureAction[T] private[spark](jobWaiter: JobWaiter[_], resultFunc:
     }
   }
 
-  def jobIds = Seq(jobWaiter.jobId)
+  def jobIds: Seq[Int] = Seq(jobWaiter.jobId)
 }
 
 
@@ -276,7 +276,7 @@ class ComplexFutureAction[T] extends FutureAction[T] {
 
   override def value: Option[Try[T]] = p.future.value
 
-  def jobIds = jobs
+  def jobIds: Seq[Int] = jobs
 
 }
 

core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala

@@ -65,7 +65,7 @@ private[spark] class HeartbeatReceiver(sc: SparkContext, scheduler: TaskSchedule
     super.preStart()
   }
 
-  override def receiveWithLogging = {
+  override def receiveWithLogging: PartialFunction[Any, Unit] = {
     case Heartbeat(executorId, taskMetrics, blockManagerId) =>
       val unknownExecutor = !scheduler.executorHeartbeatReceived(
         executorId, taskMetrics, blockManagerId)

core/src/main/scala/org/apache/spark/MapOutputTracker.scala

@@ -43,7 +43,7 @@ private[spark] class MapOutputTrackerMasterActor(tracker: MapOutputTrackerMaster
   extends Actor with ActorLogReceive with Logging {
   val maxAkkaFrameSize = AkkaUtils.maxFrameSizeBytes(conf)
 
-  override def receiveWithLogging = {
+  override def receiveWithLogging: PartialFunction[Any, Unit] = {
     case GetMapOutputStatuses(shuffleId: Int) =>
       val hostPort = sender.path.address.hostPort
       logInfo("Asked to send map output locations for shuffle " + shuffleId + " to " + hostPort)

core/src/main/scala/org/apache/spark/Partitioner.scala

@@ -76,7 +76,7 @@ object Partitioner {
  * produce an unexpected or incorrect result.
  */
 class HashPartitioner(partitions: Int) extends Partitioner {
-  def numPartitions = partitions
+  def numPartitions: Int = partitions
 
   def getPartition(key: Any): Int = key match {
     case null => 0
@@ -154,7 +154,7 @@ class RangePartitioner[K : Ordering : ClassTag, V](
     }
   }
 
-  def numPartitions = rangeBounds.length + 1
+  def numPartitions: Int = rangeBounds.length + 1
 
   private var binarySearch: ((Array[K], K) => Int) = CollectionsUtils.makeBinarySearch[K]
 

core/src/main/scala/org/apache/spark/SerializableWritable.scala

@@ -28,8 +28,10 @@ import org.apache.spark.util.Utils
 
 @DeveloperApi
 class SerializableWritable[T <: Writable](@transient var t: T) extends Serializable {
-  def value = t
-  override def toString = t.toString
+
+  def value: T = t
+
+  override def toString: String = t.toString
 
   private def writeObject(out: ObjectOutputStream): Unit = Utils.tryOrIOException {
     out.defaultWriteObject()

core/src/main/scala/org/apache/spark/SparkConf.scala

@@ -133,7 +133,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging {
   }
 
   /** Set multiple parameters together */
-  def setAll(settings: Traversable[(String, String)]) = {
+  def setAll(settings: Traversable[(String, String)]): SparkConf = {
     this.settings.putAll(settings.toMap.asJava)
     this
   }

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -986,15 +986,15 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
     union(Seq(first) ++ rest)
 
   /** Get an RDD that has no partitions or elements. */
-  def emptyRDD[T: ClassTag] = new EmptyRDD[T](this)
+  def emptyRDD[T: ClassTag]: EmptyRDD[T] = new EmptyRDD[T](this)
 
   // Methods for creating shared variables
 
   /**
    * Create an [[org.apache.spark.Accumulator]] variable of a given type, which tasks can "add"
    * values to using the `+=` method. Only the driver can access the accumulator's `value`.
    */
-  def accumulator[T](initialValue: T)(implicit param: AccumulatorParam[T]) =
+  def accumulator[T](initialValue: T)(implicit param: AccumulatorParam[T]): Accumulator[T] =
   {
     val acc = new Accumulator(initialValue, param)
     cleaner.foreach(_.registerAccumulatorForCleanup(acc))
@@ -1006,7 +1006,8 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
    * in the Spark UI. Tasks can "add" values to the accumulator using the `+=` method. Only the
    * driver can access the accumulator's `value`.
    */
-  def accumulator[T](initialValue: T, name: String)(implicit param: AccumulatorParam[T]) = {
+  def accumulator[T](initialValue: T, name: String)(implicit param: AccumulatorParam[T])
+    : Accumulator[T] = {
     val acc = new Accumulator(initialValue, param, Some(name))
     cleaner.foreach(_.registerAccumulatorForCleanup(acc))
     acc
@@ -1018,7 +1019,8 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
    * @tparam R accumulator result type
    * @tparam T type that can be added to the accumulator
    */
-  def accumulable[R, T](initialValue: R)(implicit param: AccumulableParam[R, T]) = {
+  def accumulable[R, T](initialValue: R)(implicit param: AccumulableParam[R, T])
+    : Accumulable[R, T] = {
     val acc = new Accumulable(initialValue, param)
     cleaner.foreach(_.registerAccumulatorForCleanup(acc))
     acc
@@ -1031,7 +1033,8 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
    * @tparam R accumulator result type
    * @tparam T type that can be added to the accumulator
    */
-  def accumulable[R, T](initialValue: R, name: String)(implicit param: AccumulableParam[R, T]) = {
+  def accumulable[R, T](initialValue: R, name: String)(implicit param: AccumulableParam[R, T])
+    : Accumulable[R, T] = {
     val acc = new Accumulable(initialValue, param, Some(name))
     cleaner.foreach(_.registerAccumulatorForCleanup(acc))
     acc
@@ -1209,7 +1212,7 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
   override def killExecutor(executorId: String): Boolean = super.killExecutor(executorId)
 
   /** The version of Spark on which this application is running. */
-  def version = SPARK_VERSION
+  def version: String = SPARK_VERSION
 
   /**
    * Return a map from the slave to the max memory available for caching and the remaining
@@ -1659,7 +1662,7 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
     }
   }
 
-  def getCheckpointDir = checkpointDir
+  def getCheckpointDir: Option[String] = checkpointDir
 
   /** Default level of parallelism to use when not given by user (e.g. parallelize and makeRDD). */
   def defaultParallelism: Int = {
@@ -1900,28 +1903,28 @@ object SparkContext extends Logging {
     "backward compatibility.", "1.3.0")
   object DoubleAccumulatorParam extends AccumulatorParam[Double] {
     def addInPlace(t1: Double, t2: Double): Double = t1 + t2
-    def zero(initialValue: Double) = 0.0
+    def zero(initialValue: Double): Double = 0.0
   }
 
   @deprecated("Replaced by implicit objects in AccumulatorParam. This is kept here only for " +
     "backward compatibility.", "1.3.0")
   object IntAccumulatorParam extends AccumulatorParam[Int] {
     def addInPlace(t1: Int, t2: Int): Int = t1 + t2
-    def zero(initialValue: Int) = 0
+    def zero(initialValue: Int): Int = 0
   }
 
   @deprecated("Replaced by implicit objects in AccumulatorParam. This is kept here only for " +
     "backward compatibility.", "1.3.0")
   object LongAccumulatorParam extends AccumulatorParam[Long] {
-    def addInPlace(t1: Long, t2: Long) = t1 + t2
-    def zero(initialValue: Long) = 0L
+    def addInPlace(t1: Long, t2: Long): Long = t1 + t2
+    def zero(initialValue: Long): Long = 0L
   }
 
   @deprecated("Replaced by implicit objects in AccumulatorParam. This is kept here only for " +
     "backward compatibility.", "1.3.0")
   object FloatAccumulatorParam extends AccumulatorParam[Float] {
-    def addInPlace(t1: Float, t2: Float) = t1 + t2
-    def zero(initialValue: Float) = 0f
+    def addInPlace(t1: Float, t2: Float): Float = t1 + t2
+    def zero(initialValue: Float): Float = 0f
   }
 
   // The following deprecated functions have already been moved to `object RDD` to
@@ -1931,18 +1934,18 @@ object SparkContext extends Logging {
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
   def rddToPairRDDFunctions[K, V](rdd: RDD[(K, V)])
-      (implicit kt: ClassTag[K], vt: ClassTag[V], ord: Ordering[K] = null) = {
+      (implicit kt: ClassTag[K], vt: ClassTag[V], ord: Ordering[K] = null): PairRDDFunctions[K, V] =
     RDD.rddToPairRDDFunctions(rdd)
-  }
 
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
-  def rddToAsyncRDDActions[T: ClassTag](rdd: RDD[T]) = RDD.rddToAsyncRDDActions(rdd)
+  def rddToAsyncRDDActions[T: ClassTag](rdd: RDD[T]): AsyncRDDActions[T] =
+    RDD.rddToAsyncRDDActions(rdd)
 
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
   def rddToSequenceFileRDDFunctions[K <% Writable: ClassTag, V <% Writable: ClassTag](
-      rdd: RDD[(K, V)]) = {
+      rdd: RDD[(K, V)]): SequenceFileRDDFunctions[K, V] = {
     val kf = implicitly[K => Writable]
     val vf = implicitly[V => Writable]
     // Set the Writable class to null and `SequenceFileRDDFunctions` will use Reflection to get it
@@ -1954,16 +1957,17 @@ object SparkContext extends Logging {
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
   def rddToOrderedRDDFunctions[K : Ordering : ClassTag, V: ClassTag](
-      rdd: RDD[(K, V)]) =
+      rdd: RDD[(K, V)]): OrderedRDDFunctions[K, V, (K, V)] =
     RDD.rddToOrderedRDDFunctions(rdd)
 
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
-  def doubleRDDToDoubleRDDFunctions(rdd: RDD[Double]) = RDD.doubleRDDToDoubleRDDFunctions(rdd)
+  def doubleRDDToDoubleRDDFunctions(rdd: RDD[Double]): DoubleRDDFunctions =
+    RDD.doubleRDDToDoubleRDDFunctions(rdd)
 
   @deprecated("Replaced by implicit functions in the RDD companion object. This is " +
     "kept here only for backward compatibility.", "1.3.0")
-  def numericRDDToDoubleRDDFunctions[T](rdd: RDD[T])(implicit num: Numeric[T]) =
+  def numericRDDToDoubleRDDFunctions[T](rdd: RDD[T])(implicit num: Numeric[T]): DoubleRDDFunctions =
     RDD.numericRDDToDoubleRDDFunctions(rdd)
 
   // The following deprecated functions have already been moved to `object WritableFactory` to
@@ -2134,7 +2138,7 @@ object SparkContext extends Logging {
         (backend, scheduler)
 
       case LOCAL_N_REGEX(threads) =>
-        def localCpuCount = Runtime.getRuntime.availableProcessors()
+        def localCpuCount: Int = Runtime.getRuntime.availableProcessors()
         // local[*] estimates the number of cores on the machine; local[N] uses exactly N threads.
         val threadCount = if (threads == "*") localCpuCount else threads.toInt
         if (threadCount <= 0) {
@@ -2146,7 +2150,7 @@ object SparkContext extends Logging {
         (backend, scheduler)
 
       case LOCAL_N_FAILURES_REGEX(threads, maxFailures) =>
-        def localCpuCount = Runtime.getRuntime.availableProcessors()
+        def localCpuCount: Int = Runtime.getRuntime.availableProcessors()
         // local[*, M] means the number of cores on the computer with M failures
         // local[N, M] means exactly N threads with M failures
         val threadCount = if (threads == "*") localCpuCount else threads.toInt

core/src/main/scala/org/apache/spark/TaskState.scala

@@ -27,9 +27,9 @@ private[spark] object TaskState extends Enumeration {
 
   type TaskState = Value
 
-  def isFailed(state: TaskState) = (LOST == state) || (FAILED == state)
+  def isFailed(state: TaskState): Boolean = (LOST == state) || (FAILED == state)
 
-  def isFinished(state: TaskState) = FINISHED_STATES.contains(state)
+  def isFinished(state: TaskState): Boolean = FINISHED_STATES.contains(state)
 
   def toMesos(state: TaskState): MesosTaskState = state match {
     case LAUNCHING => MesosTaskState.TASK_STARTING

core/src/main/scala/org/apache/spark/TestUtils.scala

@@ -107,7 +107,7 @@ private[spark] object TestUtils {
 
   private class JavaSourceFromString(val name: String, val code: String)
     extends SimpleJavaFileObject(createURI(name), SOURCE) {
-    override def getCharContent(ignoreEncodingErrors: Boolean) = code
+    override def getCharContent(ignoreEncodingErrors: Boolean): String = code
   }
 
   /** Creates a compiled class with the given name. Class file will be placed in destDir. */

core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala

@@ -179,7 +179,7 @@ class JavaRDD[T](val rdd: RDD[T])(implicit val classTag: ClassTag[T])
   def subtract(other: JavaRDD[T], p: Partitioner): JavaRDD[T] =
     wrapRDD(rdd.subtract(other, p))
 
-  override def toString = rdd.toString
+  override def toString: String = rdd.toString
 
   /** Assign a name to this RDD */
   def setName(name: String): JavaRDD[T] = {

core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala

@@ -108,7 +108,7 @@ class JavaSparkContext(val sc: SparkContext)
 
   private[spark] val env = sc.env
 
-  def statusTracker = new JavaSparkStatusTracker(sc)
+  def statusTracker: JavaSparkStatusTracker = new JavaSparkStatusTracker(sc)
 
   def isLocal: java.lang.Boolean = sc.isLocal