package org.slp;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper;import java.io.IOException;import java.util.StringTokenizer;/** * Created by sanglp on 2017/7/17. */public class Test2Mapper extends Mapper
     
       {    @Override    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {        //super.map(key, value, context);        String line = value.toString();//一行数据代表一组好友关系        String[] ss = line.split("\t");        context.write(new Text(ss[0]),new Text(ss[1]));//主从分成两行输出        context.write(new Text(ss[1]),new Text(ss[0]));    }}
     

package org.slp;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Reducer;import java.io.IOException;import java.util.HashSet;import java.util.Iterator;import java.util.Set;/** * Created by sanglp on 2017/7/17. */public class Test2Reduce extends Reducer
     
       {    @Override    protected void reduce(Text key, Iterable
      
        values, Context context) throws IOException, InterruptedException {        //super.reduce(key, values, context);        Set
       
         set = new HashSet
        
         ();        for(Text t :values ){            set.add(t.toString());        }        if (set.size()>1){            for(Iterator j = set.iterator();j.hasNext();){                String name = (String)j.next();                for(Iterator k = set.iterator();k.hasNext();){                    String other = (String)k.next();                    if(!name.equals(other)){                        context.write(new Text(name),new Text(other));                    }                }            }        }    }}
        
       
      
     

package org.slp;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.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import java.io.IOException;/** * Created by sanglp on 2017/7/17. */public class JobRun2 {    public static void main(String[] args){        Configuration conf = new Configuration();        conf.set("mapred.job.tracker","node1:9001");        conf.set("mapred.job.tracker","node1:9001");        conf.set("mapred.jar","C:\\Users\\sanglp\\qq.jar");        try {            Job job = new Job(conf);            job.setJobName("qq");            job.setJarByClass(JobRun2.class);            job.setMapperClass(Test2Mapper.class);            job.setReducerClass(Test2Reduce.class);            job.setMapOutputKeyClass(Text.class);            job.setMapOutputValueClass(Text.class);            job.setNumReduceTasks(1);//设置reduce任务的个数            //mapreduce输入数据所在目录或文件            FileInputFormat.addInputPath(job,new Path("/usr/input/qq"));            //mr执行之后的输出数据的目录            FileOutputFormat.setOutputPath(job,new Path("/usr/out/qq"));            try {                System.exit(job.waitForCompletion(true)?0:1);            } catch (InterruptedException e) {                e.printStackTrace();            } catch (ClassNotFoundException e) {                e.printStackTrace();            }        } catch (IOException e) {            e.printStackTrace();        }    }}

文件内容例如：

小明  小李

小花  小白