Update JavaSparkContextVarargsWorkaround.java

core/src/main/java/org/apache/spark/api/java/JavaSparkContextVarargsWorkaround.java

@@ -29,21 +29,15 @@ public final <T> JavaRDD<T> union(JavaRDD<T>... rdds) {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    List<JavaRDD<T>> rest = new ArrayList<>(rdds.length - 1);
-    for (int i = 1; i < rdds.length; i++) {
-      rest.add(rdds[i]);
-    }
+    rest = populateRDDList(rdds);
     return union(rdds[0], rest);
   }
 
   public JavaDoubleRDD union(JavaDoubleRDD... rdds) {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    List<JavaDoubleRDD> rest = new ArrayList<>(rdds.length - 1);
-    for (int i = 1; i < rdds.length; i++) {
-      rest.add(rdds[i]);
-    }
+    rest = populateRDDList(rdds);
     return union(rdds[0], rest);
   }
 
@@ -52,11 +46,16 @@ public final <K, V> JavaPairRDD<K, V> union(JavaPairRDD<K, V>... rdds) {
     if (rdds.length == 0) {
       throw new IllegalArgumentException("Union called on empty list");
     }
-    List<JavaPairRDD<K, V>> rest = new ArrayList<>(rdds.length - 1);
+    rest = populateRDDList(rdds);
+    return union(rdds[0], rest);
+  }
+
+  private static final <T> List<T> populateRDDList(T[] rdds) {
+    List<T> rest = new ArrayList<>(rdds.length - 1);
     for (int i = 1; i < rdds.length; i++) {
       rest.add(rdds[i]);
     }
-    return union(rdds[0], rest);
+    return rdds;
   }
 
   // These methods take separate "first" and "rest" elements to avoid having the same type erasure