/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.giraph.edge;

 import org.apache.hadoop.io.NullWritable;

 import org.apache.hadoop.io.WritableComparable;

 /**

  * An edge that has no value.

  *

  * @param <I> Vertex ID

  */

 public class EdgeNoValue<I extends WritableComparable>

     implements ReusableEdge<I, NullWritable> {

   /** Target vertex id */

   private I targetVertexId = null;

   /** Empty constructor */

   EdgeNoValue() { }

   /**

    * Constructor with target vertex ID. Don't call, use EdgeFactory instead.

    *

    * @param targetVertexId vertex ID

    */

   EdgeNoValue(I targetVertexId) {

     this.targetVertexId = targetVertexId;

   }

   @Override

   public void setTargetVertexId(I targetVertexId) {

     this.targetVertexId = targetVertexId;

   }

   @Override

   public void setValue(NullWritable value) {

     // do nothing

   }

   @Override

   public I getTargetVertexId() {

     return targetVertexId;

   }

   @Override

   public NullWritable getValue() {

     return NullWritable.get();

   }

   @Override

   public String toString() {

     return "(targetVertexId = " + targetVertexId + ")";

   }

 }