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}