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);  }}