Add JavaRDDLike.keyBy.

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

@@ -298,4 +298,12 @@ trait JavaRDDLike[T, This <: JavaRDDLike[T, This]] extends Serializable {
    * Save this RDD as a SequenceFile of serialized objects.
    */
   def saveAsObjectFile(path: String) = rdd.saveAsObjectFile(path)
+
+  /**
+   * Creates tuples of the elements in this RDD by applying `f`.
+   */
+  def keyBy[K](f: JFunction[T, K]): JavaPairRDD[K, T] = {
+    implicit val kcm: ClassManifest[K] = implicitly[ClassManifest[AnyRef]].asInstanceOf[ClassManifest[K]]
+    JavaPairRDD.fromRDD(rdd.keyBy(f))
+  }
 }

core/src/test/scala/spark/JavaAPISuite.java

@@ -629,4 +629,16 @@ public class JavaAPISuite implements Serializable {
     floatAccum.setValue(5.0f);
     Assert.assertEquals((Float) 5.0f, floatAccum.value());
   }
+
+  @Test
+  public void keyBy() {
+    JavaRDD<Integer> rdd = sc.parallelize(Arrays.asList(1, 2));
+    List<Tuple2<String, Integer>> s = rdd.keyBy(new Function<Integer, String>() {
+      public String call(Integer t) throws Exception {
+        return t.toString();
+      }
+    }).collect();
+    Assert.assertEquals(new Tuple2<String, Integer>("1", 1), s.get(0));
+    Assert.assertEquals(new Tuple2<String, Integer>("2", 2), s.get(1));
+  }
 }