| PropertyChangeListener | A PropertyChangeListener can subscribe with a event source. | 
| IndexedPropertyChangeEvent | A type of PropertyChangeEvent that indicates that an indexed property
 has changed.  | 
          
| PropertyChangeEvent | An event that indicates that a constraint or a boundary of a property has changed. | 
| PropertyChangeListenerProxy | The implementation of this listener proxy just delegates the received events to its listener. | 
| PropertyChangeSupport | This utility class |