public void addPropertyChangeListener(PropertyChangeListener listener){
  if (accessibleChangeSupport == null) {
    accessibleChangeSupport=new PropertyChangeSupport(this);
  }
  accessibleChangeSupport.addPropertyChangeListener(listener);
}

public void addPropertyChangeListener ( PropertyChangeListener listener ) { if ( accessibleChangeSupport == null ) { accessibleChangeSupport = new PropertyChangeSupport ( this ) ; } accessibleChangeSupport . addPropertyChangeListener ( listener ) ; }
adds a propertychangelistener to the listener list . the listener is registered for all accessible properties and will be called when those properties change .
