public class JoinMapper extends Mapper<LongWritable, Text, Text, Text> {
private Text keyEmit = new Text();
private Text valEmit = new Text();
public void map(LongWritable k, Text value, Context context) throws IOException, InterruptedException
{
 String line=value.toString();
 String[] words=line.split(",");
 keyEmit.set(words[0]);
 valEmit.set(words[1]);
 context.write(keyEmit, valEmit);
}