ui/src/main/java/ucar/util/prefs/ui/Field.java
protected void sendEvent() {
    if (listenerList != null) {
      PropertyChangeEvent event = new PropertyChangeEvent(this, name, previousValue, getValue());
      Object[] listeners = listenerList.getListenerList();
      for (int i=listeners.length-2; i>=0; i-=2)
        ((PropertyChangeListener)listeners[i+1]).propertyChange(event);
    }
  }
protected void sendEvent() {
    if (listenerList != null) {
      PropertyChangeEvent event = new PropertyChangeEvent(this, name, previousValue, getValue());
      Object[] listeners = listenerList.getListenerList();
      for (int i=listeners.length-2; i>=0; i-=2)
        ((PropertyChangeListener)listeners[i+1]).propertyChange(event);
    }
  }
send PropertyChangeEvent