code: public void firePropertyChange(String propertyName, Object oldValue, Object newValue) {
  		firePropertyChange(new PropertyChangeEvent(source, propertyName, oldValue, newValue));
  	}
docs: Report a bound property update to any registered listeners. No event is
  fired if old and new are equal and non-null.
  
  @param propertyName The programmatic name of the property that was
  changed.
  @param oldValue The old value of the property.
  @param newValue The new value of the property.