Add comment in GroupOperation for javadoc

Change-Id: Idef516e9e7af3d8fdb94ba3d13da8bb614e12c55
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
index 42ef9dd..c60b6dc 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
@@ -149,6 +149,14 @@
 
     }
 
+    /**
+     * Creates failure group operation object by setting failure code
+     * to inform the failure reason.
+     *
+     * @param groupOperation the original group operation
+     * @param failureCode failure code for a failed group operation
+     * @return failed group operation object
+     */
     public static GroupOperation createFailedGroupOperation(GroupOperation groupOperation,
                                                             GroupMsgErrorCode failureCode) {
         checkNotNull(groupOperation);