mapreduce实现QQ好友推荐

文件

hadoop hello

hdfs world
tom cat
cat dog
hello world

hello hdfs

输出

tom dog
dog tom
hello world
world hello
hdfs world
hdfs hadoop
world hdfs
world hadoop
hadoop hdfs
hadoop world
hello hdfs
hdfs hello

public class QQMapper extends Mapper<LongWritable, Text, Text, Text> {      @Override      protected void map(LongWritable key, Text value, Context context)              throws IOException, InterruptedException {            String line = value.toString();          String[] ss = StringUtils.split(line, "\\s+");            context.write(new Text(ss[0]), new Text(ss[1]));          context.write(new Text(ss[1]), new Text(ss[0]));        }    }  

public class QQReducer extends Reducer<Text, Text, Text, Text> {      @Override      protected void reduce(Text key, Iterable<Text> values, Context context)              throws IOException, InterruptedException {          Set<String> set = new HashSet<String>();            for (Text text : values) {              set.add(text.toString());          }                 if (set.size() > 1) {              for (Iterator j = set.iterator(); j.hasNext();) {                  String name =  j.next();                  for (Iterator i = set.iterator(); i.hasNext();) {                      String other =  i.next();                      if (!name.equals(other)) {                          context.write(new Text(name), new Text(other));                      }                  }                }          }      }  }