package com.micmiu.mr;
/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
public class WordCount {
 public static class TokenizerMapper 
 extends Mapper{
 private final static IntWritable one = new IntWritable(1);
 private Text word = new Text();
 public void map(Object key, Text value, Context context
 ) throws IOException, InterruptedException {
 StringTokenizer itr = new StringTokenizer(value.toString());
 while (itr.hasMoreTokens()) {
 word.set(itr.nextToken());
 context.write(word, one);
 }
 }
 }
 public static class IntSumReducer 
 extends Reducer {
 private IntWritable result = new IntWritable();
 public void reduce(Text key, Iterable values, 
 Context context
 ) throws IOException, InterruptedException {
 int sum = 0;
 for (IntWritable val : values) {
 sum += val.get();
 }
 result.set(sum);
 context.write(key, result);
 }
 }
 public static void main(String[] args) throws Exception {
 Configuration conf = new Configuration();
 String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
 if (otherArgs.length != 2) {
 System.err.println("Usage: wordcount  ");
 System.exit(2);
 }
 //conf.set("fs.defaultFS", "hdfs://192.168.6.77:9000");
 Job job = new Job(conf, "word count");
 job.setJarByClass(WordCount.class);
 job.setMapperClass(TokenizerMapper.class);
 job.setCombinerClass(IntSumReducer.class);
 job.setReducerClass(IntSumReducer.class);
 job.setOutputKeyClass(Text.class);
 job.setOutputValueClass(IntWritable.class);
 FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
 FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
 System.exit(job.waitForCompletion(true) ? 0 : 1);
 }
}

Hi Michael welcome to Hadoop 
more see micmiu.com

Hi Michael welcome to BigData
more see micmiu.com

Hi Michael welcome to Spark 
more see micmiu.com

micmiu-mbp:Downloads micmiu$ hdfs dfs -copyFromLocal micmiu-*.txt /user/micmiu/test/input
micmiu-mbp:Downloads micmiu$ hdfs dfs -ls /user/micmiu/test/input
Found 3 items
-rw-r--r-- 1 micmiu supergroup 50 2014-04-15 14:53 /user/micmiu/test/input/micmiu-01.txt
-rw-r--r-- 1 micmiu supergroup 50 2014-04-15 14:53 /user/micmiu/test/input/micmiu-02.txt
-rw-r--r-- 1 micmiu supergroup 49 2014-04-15 14:53 /user/micmiu/test/input/micmiu-03.txt
micmiu-mbp:Downloads micmiu$

原文地址：eclipse中开发Hadoop2.x的Map/Reduce项目, 感谢原作者分享。