code: public SamzaSystemStream addDestination(StreamDestination destination) {
  		PartitioningScheme scheme = destination.getPartitioningScheme();
  		int parallelism = destination.getParallelism();
  		
  		SamzaSystemStream resultStream = null;
  		for (int i=0; i<systemStreams.size(); i++) {
  			// There is an existing SystemStream that matches the settings. 
  			// Do not create a new one
  			if (systemStreams.get(i).isSame(scheme, parallelism)) {
  				resultStream = systemStreams.get(i);
  			}
  		}
  		
  		// No existing SystemStream match the requirement
  		// Create a new one 
  		if (resultStream == null) {
  			String topicName = this.getStreamId() + "-" + Integer.toString(systemStreams.size());
  			resultStream = new SamzaSystemStream(this.systemName,topicName,scheme,parallelism);
  			systemStreams.add(resultStream);
  		}
  		
  		return resultStream;
  	}
docs: /*
  Add the PI to the list of destinations.
  Return the name of the corresponding SystemStream.