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);

     }

 }