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copied!<p>I'd recommend avoiding using the <code>Observable</code> class altogether, but rather <strong>define event-specific listeners and corresponding event definitions</strong>. Then define a list of listeners within your class along with methods to add and remove listeners, and propagate events to them (see below).</p> <p><code>Observable</code> forces you to use <code>java.lang.Object</code> to represent events and then check the event type using <code>instanceof</code>, which is an ugly non-OO approach, and makes the code more difficult to understand. If you look at the classes within the javax.swing package you'll see they avoided using <code>Observer</code> / <code>Observable</code> altogether and used an approach similar to the below.</p> <p><strong>Event Definition</strong></p> <pre><code>public class MyChangeEvent extends EventObject { // This event definition is stateless but you could always // add other information here. public MyChangeEvent(Object source) { super(source); } } </code></pre> <p><strong>Listener Definition</strong></p> <pre><code>public interface MyChangeListener { public void changeEventReceived(MyChangeEvent evt); } </code></pre> <p><strong>Class Definition</strong></p> <pre><code>public class MyClass { // Use CopyOnWriteArrayList to avoid ConcurrentModificationExceptions if a // listener attempts to remove itself during event notification. private final CopyOnWriteArrayList<MyChangeListener> listeners; public class MyClass() { this.listeners = new CopyOnWriteArrayList<MyChangeListener>(); } public void addMyChangeListener(MyChangeListener l) { this.listeners.add(l); } public void removeMyChangeListener(MyChangeListener l) { this.listeners.remove(l); } // Event firing method. Called internally by other class methods. protected void fireChangeEvent() { MyChangeEvent evt = new MyChangeEvent(this); for (MyChangeListener l : listeners) { l.changeEventReceived(evt); } } } </code></pre>

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