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));
}
}

}
}
}
}