001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapreduce.lib.aggregate;
020
021import java.util.ArrayList;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025
026/**
027 * This class implements a value aggregator that sums up 
028 * a sequence of long values.
029 * 
030 */
031@InterfaceAudience.Public
032@InterfaceStability.Stable
033public class LongValueSum implements ValueAggregator<String> {
034
035  long sum = 0;
036    
037  /**
038   *  the default constructor
039   *
040   */
041  public LongValueSum() {
042    reset();
043  }
044
045  /**
046   * add a value to the aggregator
047   * 
048   * @param val
049   *          an object whose string representation represents a long value.
050   * 
051   */
052  public void addNextValue(Object val) {
053    this.sum += Long.parseLong(val.toString());
054  }
055    
056  /**
057   * add a value to the aggregator
058   * 
059   * @param val
060   *          a long value.
061   * 
062   */
063  public void addNextValue(long val) {
064    this.sum += val;
065  }
066    
067  /**
068   * @return the aggregated value
069   */
070  public long getSum() {
071    return this.sum;
072  }
073    
074  /**
075   * @return the string representation of the aggregated value
076   */
077  public String getReport() {
078    return ""+sum;
079  }
080
081  /**
082   * reset the aggregator
083   */
084  public void reset() {
085    sum = 0;
086  }
087
088  /**
089   * @return return an array of one element. The element is a string
090   *         representation of the aggregated value. The return value is
091   *         expected to be used by the a combiner.
092   */
093  public ArrayList<String> getCombinerOutput() {
094    ArrayList<String> retv = new ArrayList<String>(1);
095    retv.add(""+sum);
096    return retv;
097  }
098}
099
100