question: protected void fireVetoableChange ( String propertyName , Object oldValue , Object newValue ) throws PropertyVetoException { if ( oldValue == newValue ) { return ; } VetoableChangeSupport vetoableSupport = this . vetoableSupport ; if ( vetoableSupport != null ) { vetoableSupport . fireVetoableChange ( propertyName , oldValue , newValue ) ; } }
target:  Fires a PropertyChangeEvent in response to a change in a vetoable property. The event will be delivered to all registered VetoableChangeListeners. If a VetoableChangeListener throws a PropertyVetoException, a new event is fired reverting all VetoableChangeListeners to the old value and the exception is then rethrown. No event will be delivered if oldValue and newValue are the same.