@Override
	public Observable<E> addObserver(Observer<E> observer) {
		if(observer != null) {
			observers.add(observer);
		}
		return this;
	}
@ Override public Observable < E > addObserver ( Observer < E > observer ) { if ( observer != null ) { observers . add ( observer ) ; } return this ; }
@see org.dihedron.patterns.observer.Observable#addObserver(org.dihedron.patterns.observer.Observer)