IT

Interfaces

• An interface can extend another interface:

public interface IQuackable extends IQuackObservable {
    public void quack();
}

For "each"

private ArrayList <IBeatObserver> beatObservers = new ArrayList<IBeatObserver>();
for(IBeatObserver o : beatObservers)
           o.updateBeat();

ArrayList Vs Vector

Main difference: ArrayList is not synchronized (not thread safe) and (because of this) is faster than Vector. Vector is thread safe and slower than ArrayList.