public void fireStateChanged(){
  ChangeEvent e=new ChangeEvent(this);
  for (  ChangeListener listener : listeners) {
    listener.stateChanged(e);
  }
}

public void fireStateChanged ( ) { ChangeEvent e = new ChangeEvent ( this ) ; for ( ChangeListener listener : listeners ) { listener . stateChanged ( e ) ; } }
should be called whenever a field was updated
