[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.

11 files changed, 28 insertions, 29 deletions

diff --git a/graphx/src/main/scala/org/apache/spark/graphx/EdgeContext.scala b/graphx/src/main/scala/org/apache/spark/graphx/EdgeContext.scala
index d8be02e202..23430179f1 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/EdgeContext.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/EdgeContext.scala
@@ -62,7 +62,6 @@ object EdgeContext {
    *    , _ + _)
    * }}}
    */
-  def unapply[VD, ED, A](edge: EdgeContext[VD, ED, A]) =
+  def unapply[VD, ED, A](edge: EdgeContext[VD, ED, A]): Some[(VertexId, VertexId, VD, VD, ED)] =
     Some(edge.srcId, edge.dstId, edge.srcAttr, edge.dstAttr, edge.attr)
 }
-
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/EdgeDirection.scala b/graphx/src/main/scala/org/apache/spark/graphx/EdgeDirection.scala
index 6f03eb1439..058c8c8aa1 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/EdgeDirection.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/EdgeDirection.scala
@@ -34,12 +34,12 @@ class EdgeDirection private (private val name: String) extends Serializable {
 
   override def toString: String = "EdgeDirection." + name
 
-  override def equals(o: Any) = o match {
+  override def equals(o: Any): Boolean = o match {
     case other: EdgeDirection => other.name == name
     case _ => false
   }
 
-  override def hashCode = name.hashCode
+  override def hashCode: Int = name.hashCode
 }
 
 
@@ -48,14 +48,14 @@ class EdgeDirection private (private val name: String) extends Serializable {
  */
 object EdgeDirection {
   /** Edges arriving at a vertex. */
-  final val In = new EdgeDirection("In")
+  final val In: EdgeDirection = new EdgeDirection("In")
 
   /** Edges originating from a vertex. */
-  final val Out = new EdgeDirection("Out")
+  final val Out: EdgeDirection = new EdgeDirection("Out")
 
   /** Edges originating from *or* arriving at a vertex of interest. */
-  final val Either = new EdgeDirection("Either")
+  final val Either: EdgeDirection = new EdgeDirection("Either")
 
   /** Edges originating from *and* arriving at a vertex of interest. */
-  final val Both = new EdgeDirection("Both")
+  final val Both: EdgeDirection = new EdgeDirection("Both")
 }
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/EdgeTriplet.scala b/graphx/src/main/scala/org/apache/spark/graphx/EdgeTriplet.scala
index 9d473d5ebd..c8790cac3d 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/EdgeTriplet.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/EdgeTriplet.scala
@@ -62,7 +62,7 @@ class EdgeTriplet[VD, ED] extends Edge[ED] {
   def vertexAttr(vid: VertexId): VD =
     if (srcId == vid) srcAttr else { assert(dstId == vid); dstAttr }
 
-  override def toString = ((srcId, srcAttr), (dstId, dstAttr), attr).toString()
+  override def toString: String = ((srcId, srcAttr), (dstId, dstAttr), attr).toString()
 
   def toTuple: ((VertexId, VD), (VertexId, VD), ED) = ((srcId, srcAttr), (dstId, dstAttr), attr)
 }
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
index 373af75448..c561570809 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
@@ -324,7 +324,7 @@ class EdgePartition[
    *
    * @return an iterator over edges in the partition
    */
-  def iterator = new Iterator[Edge[ED]] {
+  def iterator: Iterator[Edge[ED]] = new Iterator[Edge[ED]] {
     private[this] val edge = new Edge[ED]
     private[this] var pos = 0
 
@@ -351,7 +351,7 @@ class EdgePartition[
 
     override def hasNext: Boolean = pos < EdgePartition.this.size
 
-    override def next() = {
+    override def next(): EdgeTriplet[VD, ED] = {
       val triplet = new EdgeTriplet[VD, ED]
       val localSrcId = localSrcIds(pos)
       val localDstId = localDstIds(pos)
@@ -518,11 +518,11 @@ private class AggregatingEdgeContext[VD, ED, A](
     _attr = attr
   }
 
-  override def srcId = _srcId
-  override def dstId = _dstId
-  override def srcAttr = _srcAttr
-  override def dstAttr = _dstAttr
-  override def attr = _attr
+  override def srcId: VertexId = _srcId
+  override def dstId: VertexId = _dstId
+  override def srcAttr: VD = _srcAttr
+  override def dstAttr: VD = _dstAttr
+  override def attr: ED = _attr
 
   override def sendToSrc(msg: A) {
     send(_localSrcId, msg)
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgeRDDImpl.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgeRDDImpl.scala
index 43a3aea0f6..c88b2f65a8 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgeRDDImpl.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgeRDDImpl.scala
@@ -70,9 +70,9 @@ class EdgeRDDImpl[ED: ClassTag, VD: ClassTag] private[graphx] (
     this
   }
 
-  override def getStorageLevel = partitionsRDD.getStorageLevel
+  override def getStorageLevel: StorageLevel = partitionsRDD.getStorageLevel
 
-  override def checkpoint() = {
+  override def checkpoint(): Unit = {
     partitionsRDD.checkpoint()
   }
 
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
index 8ab255bd40..1df86449fa 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
@@ -50,7 +50,7 @@ class ReplicatedVertexView[VD: ClassTag, ED: ClassTag](
    * Return a new `ReplicatedVertexView` where edges are reversed and shipping levels are swapped to
    * match.
    */
-  def reverse() = {
+  def reverse(): ReplicatedVertexView[VD, ED] = {
     val newEdges = edges.mapEdgePartitions((pid, part) => part.reverse)
     new ReplicatedVertexView(newEdges, hasDstId, hasSrcId)
   }
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
index 349c8545bf..33ac7b0ed6 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
@@ -71,9 +71,9 @@ class VertexRDDImpl[VD] private[graphx] (
     this
   }
 
-  override def getStorageLevel = partitionsRDD.getStorageLevel
+  override def getStorageLevel: StorageLevel = partitionsRDD.getStorageLevel
 
-  override def checkpoint() = {
+  override def checkpoint(): Unit = {
     partitionsRDD.checkpoint()
   }
 
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/lib/ConnectedComponents.scala b/graphx/src/main/scala/org/apache/spark/graphx/lib/ConnectedComponents.scala
index e2f6cc1389..859f896039 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/lib/ConnectedComponents.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/lib/ConnectedComponents.scala
@@ -37,7 +37,7 @@ object ConnectedComponents {
    */
   def run[VD: ClassTag, ED: ClassTag](graph: Graph[VD, ED]): Graph[VertexId, ED] = {
     val ccGraph = graph.mapVertices { case (vid, _) => vid }
-    def sendMessage(edge: EdgeTriplet[VertexId, ED]) = {
+    def sendMessage(edge: EdgeTriplet[VertexId, ED]): Iterator[(VertexId, VertexId)] = {
       if (edge.srcAttr < edge.dstAttr) {
         Iterator((edge.dstId, edge.srcAttr))
       } else if (edge.srcAttr > edge.dstAttr) {
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/lib/LabelPropagation.scala b/graphx/src/main/scala/org/apache/spark/graphx/lib/LabelPropagation.scala
index 82e9e06515..2bcf8684b8 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/lib/LabelPropagation.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/lib/LabelPropagation.scala
@@ -43,7 +43,7 @@ object LabelPropagation {
    */
   def run[VD, ED: ClassTag](graph: Graph[VD, ED], maxSteps: Int): Graph[VertexId, ED] = {
     val lpaGraph = graph.mapVertices { case (vid, _) => vid }
-    def sendMessage(e: EdgeTriplet[VertexId, ED]) = {
+    def sendMessage(e: EdgeTriplet[VertexId, ED]): Iterator[(VertexId, Map[VertexId, VertexId])] = {
       Iterator((e.srcId, Map(e.dstAttr -> 1L)), (e.dstId, Map(e.srcAttr -> 1L)))
     }
     def mergeMessage(count1: Map[VertexId, Long], count2: Map[VertexId, Long])
@@ -54,7 +54,7 @@ object LabelPropagation {
         i -> (count1Val + count2Val)
       }.toMap
     }
-    def vertexProgram(vid: VertexId, attr: Long, message: Map[VertexId, Long]) = {
+    def vertexProgram(vid: VertexId, attr: Long, message: Map[VertexId, Long]): VertexId = {
       if (message.isEmpty) attr else message.maxBy(_._2)._1
     }
     val initialMessage = Map[VertexId, Long]()
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/lib/PageRank.scala b/graphx/src/main/scala/org/apache/spark/graphx/lib/PageRank.scala
index 570440ba44..042e366a29 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/lib/PageRank.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/lib/PageRank.scala
@@ -156,7 +156,7 @@ object PageRank extends Logging {
       (newPR, newPR - oldPR)
     }
 
-    def sendMessage(edge: EdgeTriplet[(Double, Double), Double]) = {
+    def sendMessage(edge: EdgeTriplet[(Double, Double), Double]): Iterator[(VertexId, Double)] = {
       if (edge.srcAttr._2 > tol) {
         Iterator((edge.dstId, edge.srcAttr._2 * edge.attr))
       } else {
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/util/collection/GraphXPrimitiveKeyOpenHashMap.scala b/graphx/src/main/scala/org/apache/spark/graphx/util/collection/GraphXPrimitiveKeyOpenHashMap.scala
index 57b01b6f2e..e2754ea699 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/util/collection/GraphXPrimitiveKeyOpenHashMap.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/util/collection/GraphXPrimitiveKeyOpenHashMap.scala
@@ -56,7 +56,7 @@ class GraphXPrimitiveKeyOpenHashMap[@specialized(Long, Int) K: ClassTag,
 
   private var _oldValues: Array[V] = null
 
-  override def size = keySet.size
+  override def size: Int = keySet.size
 
   /** Get the value for a given key */
   def apply(k: K): V = {
@@ -112,7 +112,7 @@ class GraphXPrimitiveKeyOpenHashMap[@specialized(Long, Int) K: ClassTag,
     }
   }
 
-  override def iterator = new Iterator[(K, V)] {
+  override def iterator: Iterator[(K, V)] = new Iterator[(K, V)] {
     var pos = 0
     var nextPair: (K, V) = computeNextPair()
 
@@ -128,9 +128,9 @@ class GraphXPrimitiveKeyOpenHashMap[@specialized(Long, Int) K: ClassTag,
       }
     }
 
-    def hasNext = nextPair != null
+    def hasNext: Boolean = nextPair != null
 
-    def next() = {
+    def next(): (K, V) = {
       val pair = nextPair
       nextPair = computeNextPair()
       pair