void addListener(JmolSelectionListener listener) {
		removeListener(listener);
		int len = listeners.length;
		for (int i = len; --i >= 0;) {
			if (listeners[i] == null) {
				listeners[i] = listener;
				return;
			}
		}
		listeners = (JmolSelectionListener[]) ArrayUtil.doubleLength(listeners);
		listeners[len] = listener;
	}