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/**
028 * This class implements a value aggregator that sums up a sequence of double
029 * values.
030 * 
031 */
032@InterfaceAudience.Public
033@InterfaceStability.Stable
034public class DoubleValueSum implements ValueAggregator<String> {
035
036  double sum = 0;
037
038  /**
039   * The default constructor
040   * 
041   */
042  public DoubleValueSum() {
043    reset();
044  }
045
046  /**
047   * add a value to the aggregator
048   * 
049   * @param val
050   *          an object whose string representation represents a double value.
051   * 
052   */
053  public void addNextValue(Object val) {
054    this.sum += Double.parseDouble(val.toString());
055  }
056
057  /**
058   * add a value to the aggregator
059   * 
060   * @param val
061   *          a double value.
062   * 
063   */
064  public void addNextValue(double val) {
065    this.sum += val;
066  }
067
068  /**
069   * @return the string representation of the aggregated value
070   */
071  public String getReport() {
072    return "" + sum;
073  }
074
075  /**
076   * @return the aggregated value
077   */
078  public double getSum() {
079    return this.sum;
080  }
081
082  /**
083   * reset the aggregator
084   */
085  public void reset() {
086    sum = 0;
087  }
088
089  /**
090   * @return return an array of one element. The element is a string
091   *         representation of the aggregated value. The return value is
092   *         expected to be used by the a combiner.
093   */
094  public ArrayList<String> getCombinerOutput() {
095    ArrayList<String> retv = new ArrayList<String>(1);
096    retv.add("" + sum);
097    return retv;
098  }
099
100}