code: protected void fireValueChange(Object oldValue, Object newValue) {
          if (hasValueChanged(oldValue, newValue)) {
              fireValueChangeEvent(oldValue, newValue);
          }
      }
docs: Notifies all listeners that have registered interest for
  notification on this event type.  The event instance
  is lazily created using the parameters passed into
  the fire method.
  
  @param oldValue the float value before the change
  @param newValue the float value after the change