Add a method to concatenate 2 TopologyBatchOperations.

Part of ONOS-1925

Change-Id: Iaa5eb561cf40491b83477bb5d46b6ebec4fec162
diff --git a/src/main/java/net/onrc/onos/core/topology/TopologyBatchOperation.java b/src/main/java/net/onrc/onos/core/topology/TopologyBatchOperation.java
index f7d7049..e8dcec7 100644
--- a/src/main/java/net/onrc/onos/core/topology/TopologyBatchOperation.java
+++ b/src/main/java/net/onrc/onos/core/topology/TopologyBatchOperation.java
@@ -49,4 +49,17 @@
                 new BatchOperationEntry<Operator, TopologyEvent>(
                                         Operator.REMOVE, topologyEvent));
     }
+
+    /**
+     * Concatenates specified TopologyBatchOperation.
+     *
+     * @param ops TopologyBatchOperation to concatenate.
+     * @return this
+     */
+    public TopologyBatchOperation concat(final TopologyBatchOperation ops) {
+        for (BatchOperationEntry<Operator, TopologyEvent> e : ops.getOperations()) {
+            this.addOperation(e);
+        }
+        return this;
+    }
 }