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
019 package org.apache.hadoop.mapreduce.lib.aggregate;
020
021 import java.util.ArrayList;
022
023 import org.apache.hadoop.classification.InterfaceAudience;
024 import 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
034 public 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 }