Minor fixes

- style: (v,null) => (v, null)
- mention the shuffle in Javadoc

Author: ash211

core/src/main/scala/org/apache/spark/rdd/RDD.scala

@@ -374,31 +374,37 @@ abstract class RDD[T: ClassTag](
   /**
    * Return the intersection of this RDD and another one. The output will not contain any duplicate
    * elements, even if the input RDDs did.
+   *
+   * Note that this method performs a shuffle internally
    */
   def intersection(other: RDD[T]): RDD[T] =
-    this.map(v => (v,null)).cogroup(other.map(v => (v,null)))
+    this.map(v => (v, null)).cogroup(other.map(v => (v, null)))
         .filter { case (_, (leftGroup, rightGroup)) => leftGroup.nonEmpty && rightGroup.nonEmpty }
         .keys
 
   /**
    * Return the intersection of this RDD and another one. The output will not contain any duplicate
    * elements, even if the input RDDs did.
    *
+   * Note that this method performs a shuffle internally
+   *
    * @param partitioner Partitioner to use for the resulting RDD
    */
   def intersection(other: RDD[T], partitioner: Partitioner): RDD[T] =
-    this.map(v => (v,null)).cogroup(other.map(v => (v,null)), partitioner)
+    this.map(v => (v, null)).cogroup(other.map(v => (v, null)), partitioner)
         .filter { case (_, (leftGroup, rightGroup)) => leftGroup.nonEmpty && rightGroup.nonEmpty }
         .keys
 
   /**
    * Return the intersection of this RDD and another one. The output will not contain any duplicate
    * elements, even if the input RDDs did.  Performs a hash partition across the cluster
    *
+   * Note that this method performs a shuffle internally
+   *
    * @param numPartitions How many partitions to use in the resulting RDD
    */
   def intersection(other: RDD[T], numPartitions: Int): RDD[T] =
-    this.map(v => (v,null)).cogroup(other.map(v => (v,null)), new HashPartitioner(numPartitions))
+    this.map(v => (v, null)).cogroup(other.map(v => (v, null)), new HashPartitioner(numPartitions))
         .filter { case (_, (leftGroup, rightGroup)) => leftGroup.nonEmpty && rightGroup.nonEmpty }
         .keys