Java/Swing JFC/EventListenerList

Use EventListenerList to store event listener list

   <source lang="java">

import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; import javax.swing.event.EventListenerList; class DualListener implements ActionListener, ChangeListener {

 public void actionPerformed(ActionEvent e) {
   System.out.println("dual: Action " + e);
 }
 public void stateChanged(ChangeEvent e) {
   System.out.println("dual: Change " + e);
 }

} public class Main {

 public Main() {
   MyObject pair = new MyObject("This is "a"", "This is "b"");
   ActionListener al = new ActionListener() {
     public void actionPerformed(ActionEvent e) {
       System.out.println("al: Action " + e);
     }
   };
   DualListener dual = new DualListener();
   pair.addActionListener(al);
   pair.addChangeListener(dual);
   pair.setA("new A");
   pair.setB("new B");
   pair.addActionListener(dual);
   pair.setA("another A");
   pair.removeActionListener(dual);
   pair.setB("another B");
   pair.setA("final A");
 }
 public static void main(String arg[]) {
   new Main();
 }

} class MyObject {

 Object a = null, b = null;
 EventListenerList events = new EventListenerList();
 ActionEvent actionEvent; 
 ChangeEvent changeEvent;  
 public MyObject(Object a1, Object b1) {
   a = a1;
   b = b1;
 }
 public void addActionListener(ActionListener listener) {
   events.add(ActionListener.class, listener);
 }
 public void removeActionListener(ActionListener listener) {
   events.remove(ActionListener.class, listener);
 }
 public void addChangeListener(ChangeListener listener) {
   events.add(ChangeListener.class, listener);
 }
 public void removeChangeListener(ChangeListener listener) {
   events.remove(ChangeListener.class, listener);
 }
 public void setA(Object newA) {
   a = newA;
   fireAChanged();
 }
 public void setB(Object newB) {
   b = newB;
   fireBChanged();
 }
 protected void fireAChanged() {
   Object[] listeners = events.getListenerList();
   for (int i = listeners.length - 2; i >= 0; i -= 2) {
     if (listeners[i] == ActionListener.class) {
       if (actionEvent == null) {
         actionEvent = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "a");
       }
       ((ActionListener) listeners[i + 1]).actionPerformed(actionEvent);
     }
   }
 }
 protected void fireBChanged() {
   Object[] listeners = events.getListenerList();
   for (int i = listeners.length - 2; i >= 0; i -= 2) {
     if (listeners[i] == ChangeListener.class) {
       if (changeEvent == null) {
         changeEvent = new ChangeEvent(this);
       }
       ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
     }
   }
 }

}

</source>