SPARK-4459 changed type parameter for groupBy from K to U.

Author: Saldanha

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

@@ -212,8 +212,8 @@ trait JavaRDDLike[T, This <: JavaRDDLike[T, This]] extends Serializable {
    * Return an RDD of grouped elements. Each group consists of a key and a sequence of elements
    * mapping to that key.
    */
-  def groupBy[K](f: JFunction[T, K]): JavaPairRDD[K, JIterable[T]] = {
-    implicit val ctagK: ClassTag[K] = fakeClassTag
+  def groupBy[U](f: JFunction[T, U]): JavaPairRDD[U, JIterable[T]] = {
+    implicit val ctagK: ClassTag[U] = fakeClassTag
     implicit val ctagV: ClassTag[JList[T]] = fakeClassTag
     JavaPairRDD.fromRDD(groupByResultToJava(rdd.groupBy(f)(fakeClassTag)))
   }
@@ -222,10 +222,10 @@ trait JavaRDDLike[T, This <: JavaRDDLike[T, This]] extends Serializable {
    * Return an RDD of grouped elements. Each group consists of a key and a sequence of elements
    * mapping to that key.
    */
-  def groupBy[K](f: JFunction[T, K], numPartitions: Int): JavaPairRDD[K, JIterable[T]] = {
-    implicit val ctagK: ClassTag[K] = fakeClassTag
+  def groupBy[U](f: JFunction[T, U], numPartitions: Int): JavaPairRDD[U, JIterable[T]] = {
+    implicit val ctagK: ClassTag[U] = fakeClassTag
     implicit val ctagV: ClassTag[JList[T]] = fakeClassTag
-    JavaPairRDD.fromRDD(groupByResultToJava(rdd.groupBy(f, numPartitions)(fakeClassTag[K])))
+    JavaPairRDD.fromRDD(groupByResultToJava(rdd.groupBy(f, numPartitions)(fakeClassTag[U])))
   }
 
   /**