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.reduce; 020 021 import java.io.IOException; 022 023 import org.apache.hadoop.classification.InterfaceAudience; 024 import org.apache.hadoop.classification.InterfaceStability; 025 import org.apache.hadoop.io.LongWritable; 026 import org.apache.hadoop.mapreduce.Reducer; 027 028 @InterfaceAudience.Public 029 @InterfaceStability.Stable 030 public class LongSumReducer<KEY> extends Reducer<KEY, LongWritable, 031 KEY,LongWritable> { 032 033 private LongWritable result = new LongWritable(); 034 035 public void reduce(KEY key, Iterable<LongWritable> values, 036 Context context) throws IOException, InterruptedException { 037 long sum = 0; 038 for (LongWritable val : values) { 039 sum += val.get(); 040 } 041 result.set(sum); 042 context.write(key, result); 043 } 044 045 }