map - Printing unique or distinct values

Question

I am new to map reduce and writing a reduce function to print the values in a Iterable. Below is my print function:

public class Reduce extends Reducer<Text, Text, Text, Text> {
  protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {

      StringBuilder builder = new StringBuilder();
        for (Text value : values) {
        builder.append("<");
          builder.append(value);
          builder.append(",");
          builder.append(key);
          builder.append(">");
          builder.append("\n");
          context.write(new Text(builder.substring(0, builder.length())), key);
        }  
  }

}

Output is:

Issue is that the values are getting repeated i.e. <2,1> is repeated 2 times... My requirement is after <2,1> I should directly get <3,1> and then <4,1>. In short all my should be unique.

My final output should be:

<2,1>
<3,1>
<4,1>
<3,2>
<4,2>
<1,2>
<4,3>

Please suggest.

Answer 1

        StringBuilder builder ;
        for (Text value : values) 
        {
          builder = new StringBuilder();
          builder.append("<");
          builder.append(value);
          builder.append(",");
          builder.append(key);
          builder.append(">");
          builder.append("\n");
          context.write(new Text(builder.substring(0, builder.length())), key);
        }  

Try this.