Building Oberver and Observable class

Question

Instead of using built in class Observable and Observer I am trying to build it myself.

From docs I figured:

public class Observable{
   private Set<Observer> observingMe=null;
   private boolean amIchanged;

   public void notifyObservers(Object args){
        for(Observer o:observingMe){
            o.update(args);
        }
   }

   public void addObserver(Observer e){
    observingMe.add(e);
   }

}

public class Price implements Observable{
    private int price;
    public void setPrice(int newPrice){
        price=newPrice;
        notifyObservers(price);
    }
}
public interface Observer{
    public void update(Object args);
}

Is this(in brief) the right implementation of Observable? What else do I need to consider while building Observable class. Is there a way to automatically detect any chane in Observable instance or the inherited class has to explicitly call notifyObservers?

Please don't mind the syntax or minor error

Dici Dici · Accepted Answer · 2015-01-03T18:10:50

In your notify method, consider the case when an observer throws an exception when the update is called. If you don't handle it, it will prevent the other observers the be notified. Moreover, you may want to notify each observer in a separate thread as one of them could take a long time to react to the event, preventing the others to be notified early.

Also, you never use your boolean amIChanged and you keep it private without a getter. Otherwise, you have the basic principle implemented.

Building Oberver and Observable class

3 Answers