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.IntWritable;
026    import org.apache.hadoop.mapreduce.Reducer;
027    
028    @InterfaceAudience.Public
029    @InterfaceStability.Stable
030    public class IntSumReducer<Key> extends Reducer<Key,IntWritable,
031                                                    Key,IntWritable> {
032      private IntWritable result = new IntWritable();
033    
034      public void reduce(Key key, Iterable<IntWritable> values, 
035                         Context context) throws IOException, InterruptedException {
036        int sum = 0;
037        for (IntWritable val : values) {
038          sum += val.get();
039        }
040        result.set(sum);
041        context.write(key, result);
042      }
043    
044    }