result = mResponseListeners.add(listener);
HashSet clone = (HashSet)mResponseListeners.clone(); result = clone.add(listener); mResponseListeners = clone;
	public boolean addResponseListener(ResponseListener listener)	{		if (null == listener)	throw new IllegalArgumentException("listener can't be null.");		boolean result = false;				synchronized (mResponseListenersMonitor)		{			if (!mResponseListeners.contains(listener))			{				result = mResponseListeners.add(listener);			}			else			{				result = true;			}		}				assert true == mResponseListeners.contains(listener);				return result;	}