Add doc

java/org/rocksdb/RocksDB.java

@@ -140,9 +140,11 @@ public class RocksDB {
    * Return a heap-allocated iterator over the contents of the database.
    * The result of newIterator() is initially invalid (caller must
    * call one of the Seek methods on the iterator before using it).
-   * 
+   *
    * Caller should close the iterator when it is no longer needed.
    * The returned iterator should be closed before this db is closed.
+   *
+   * @return instance of iterator object.
    */
   public Iterator newIterator() {
     return new Iterator(iterator0(nativeHandle_));