observablelist.java

it is whiteboard sourse code

package org.merlin.step.nov;

import java.util.*;

public class ObservableList {
  Vector list;
  
  public ObservableList () {
    list = new Vector ();
  }

  public Enumeration elements () {
    return list.elements ();
  }

  public synchronized void addElement (Object o) {
    list.addElement (o);
    fireUpdate ();
  }

  public synchronized void replaceElementAtEnd (Object o, Object n) {
    list.removeElement (o);
    addElement (n);
  }

  Vector listeners = new Vector ();

  public synchronized void addUpdateListener (UpdateListener l) {
    listeners.addElement (l);
  }

  public synchronized void removeUpdateListener (UpdateListener l) {
    listeners.removeElement (l);
  }

  void fireUpdate () {
    UpdateEvent event = new UpdateEvent (this);
    for (int i = 0; i < listeners.size (); ++ i)
      ((UpdateListener) listeners.elementAt (i)).updateOccurred (event);
  }
}