package designpatterns.observer.aspectj;import ca.ubc.cs.spl.aspectPatterns.patternLibrary.*;public aspect SongCountObserver extends ObserverProtocol {	declare parents : Song extends Subject;	declare parents : SongPlayCounter implements Observer;	pointcut titleUse(Song song) :		this(song)		&& execution(public void Song.play());	public pointcut subjectChange(Subject subject) : 		titleUse(Song) && this(subject);	public void updateObserver(Subject s, Observer o) {		SongPlayCounter counter = (SongPlayCounter) o;		counter.incrementPlays((Song) s);	}	// could be injected by a dependency injection	// framework like Spring	private SongPlayCounter defaultCounter = new SongPlayCounter();	pointcut songCreation(Subject s) :		execution(public Song.new(..))		&& this(s);	after(Subject s) returning : songCreation(s){		// different songs could be tracked in different statistical sets...		addObserver(s, defaultCounter);	}}