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.reduce;
020
021import java.io.IOException;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025import org.apache.hadoop.io.LongWritable;
026import org.apache.hadoop.mapreduce.Reducer;
027
028@InterfaceAudience.Public
029@InterfaceStability.Stable
030public 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}