mao/reduce实现求平均值

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

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.output.*;
import org.apache.hadoop.mapreduce.lib.input.*;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.util.*;
public class Score_Process extends Configured implements Tool {
    /**
     * 程序说明：主要用来实现计算学生的平均成绩。
     * 数据输入：文件形式输入，每一行包含学生姓名 学生成绩。一个学生有多门成绩则有多行。例如：张三 98
     * 数据输出：张三 84 学生姓名 学生平均成绩
     * 实现思路：在map阶段<张三，（98,68,……）>
     * **/
    
    public static class Map extends Mapper<LongWritable,Text,Text,IntWritable>{
        public void map(LongWritable key,Text value,Context context)throws IOException,InterruptedException{
            String line=value.toString();
            System.out.println(line);//测试
            StringTokenizer tokenizer=new StringTokenizer(line);
            while(tokenizer.hasMoreTokens()){
                String name=tokenizer.nextToken();
                String strscore=tokenizer.nextToken();
                int intscore=Integer.parseInt(strscore);
                context.write(new Text(name), new IntWritable(intscore));
            }
            
        }
        
    }
    
    public static class Reduce extends Reducer<Text,IntWritable,Text,IntWritable>{
        public void reduce(Text key,Iterable<IntWritable>values,Context context) throws IOException, InterruptedException{
            int sun=0,count=0;
            for(IntWritable val:values){
                sun+=val.get();
                count++;
            }
            int averscore=(int)sun/count;
            context.write(key, new IntWritable(averscore));
        }
        
    }
    
    public int run(String[] args) throws Exception{
        Job job=new Job(getConf());
        job.setJarByClass(Score_Process.class);
        job.setJobName("Score_Process");
        
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        
        job.setMapperClass(Map.class);
        //job.setCombinerClass(Reduce.class);
        job.setReducerClass(Reduce.class);
        
        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);
        
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        boolean success=job.waitForCompletion(true);
        
        return success?0:1;
    }
    
    public static void main(String[] args)throws Exception{
        int ret=ToolRunner.run(new Score_Process(), args);
        System.exit(ret);
    }

}