HAMA-921, java 7 compatible

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1630227 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/graph/src/main/java/org/apache/hama/graph/VertexMessages.java b/graph/src/main/java/org/apache/hama/graph/VertexMessages.java
index f94b9e2..bdbff1b 100644
--- a/graph/src/main/java/org/apache/hama/graph/VertexMessages.java
+++ b/graph/src/main/java/org/apache/hama/graph/VertexMessages.java
@@ -170,4 +170,9 @@
   public V getMessageVID() {
     return this.currentMessage == null ? null : (V) this.currentMessage.getVertexId();
   }
+
+  @Override
+  public void remove() {
+    throw new UnsupportedOperationException("remove");
+  }
 }