code: public static String addNamedOutput(Job job, String namedOutput, OutputFormat outputFormat,
  	    Class<?> keyClass, Class<?> valueClass) throws FileNotFoundException, IOException,
  	    URISyntaxException {
  		checkNamedOutputName(job, namedOutput, true);
  		Configuration conf = job.getConfiguration();
  		String uniqueName = UUID.randomUUID().toString() + '.' + "out-format.dat";
  		InstancesDistributor.distribute(outputFormat, uniqueName, conf);
  		conf.set(MULTIPLE_OUTPUTS, conf.get(MULTIPLE_OUTPUTS, "") + " " + namedOutput);
  		conf.set(MO_PREFIX + namedOutput + FORMAT_INSTANCE_FILE, uniqueName);
  		conf.setClass(MO_PREFIX + namedOutput + KEY, keyClass, Object.class);
  		conf.setClass(MO_PREFIX + namedOutput + VALUE, valueClass, Object.class);
  		return uniqueName;
  	}
docs: Adds a named output for the job. Returns the instance file that has been created.