code: public void addObserver(IOutputStreamObserver obs)
  	{
  		if (obs==null){
  			this.obs = obs;
  		}
  		else {
  			if (obsList==null){
  				this.obsList = new ArrayList <IOutputStreamObserver> ();
  			}
  			this.obsList.add(obs);
  		}
  	}
docs: Sets an observer for this output stream. The observer will be
  notified when the stream is first written to.