Hadoop--map/reduce实现单词计数

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapred.*;

import java.io.IOException;
import java.util.*;

public class WordCount {

    /*
     * 实现输入内容单词的计数功能
     * 一、mapper方法将输入内容处理为<key1,value1>形式
     * 二、reduce方法接收mapper的结果，将相同key1的value值相加得到单词的个数
     * 三、输出得到的结果到hdfs中
     * 
     * */
    
    //main函数
    public static void main(String[] args) throws Exception{
        JobConf conf=new JobConf(WordCount.class);
        conf.setJobName("WordCount");
        conf.setOutputKeyClass(Text.class);
        conf.setOutputValueClass(IntWritable.class);
        
        conf.setMapperClass(Map.class);
        conf.setReducerClass(Reduce.class);
        
        conf.setInputFormat(TextInputFormat.class);
        conf.setOutputFormat(TextOutputFormat.class);
        
        FileInputFormat.setInputPaths(conf,new Path(args[0]));
        FileOutputFormat.setOutputPath(conf, new Path(args[1]));
        
        JobClient.runJob(conf);
        
    }
    
    //map函数
    public static class Map extends MapReduceBase implements Mapper<LongWritable,Text,
    Text,IntWritable>{
        private final static IntWritable one=new IntWritable(1);
        private Text word=new Text();
        
        public void map(LongWritable key,Text value, 
        OutputCollector<Text,IntWritable>output,Reporter reporter)throws IOException{
            String line=value.toString();
            StringTokenizer tokenizer=new StringTokenizer(line);
            while(tokenizer.hasMoreTokens()){
                word.set(tokenizer.nextToken());
                output.collect(word, one);
                
            }
            
        }
        
    }
    
    //reduce函数
    public static class Reduce extends MapReduceBase implements Reducer<Text,IntWritable,
    Text,IntWritable>{
        public void reduce(Text key,Iterator<IntWritable>values,OutputCollector<Text,
        IntWritable>output,Reporter repoter) throws IOException{
            int sum=0;
            while(values.hasNext()){
                sum+=values.next().get();
            }
            output.collect(key,new IntWritable(sum));
        }
    }
    
    
    
}