question: protected void firePropertyChange ( String propertyName , Object oldValue , Object newValue ) { if ( oldValue == newValue ) { return ; } PropertyChangeSupport changeSupport = this . changeSupport ; if ( changeSupport != null ) { changeSupport . firePropertyChange ( propertyName , oldValue , newValue ) ; } }
target:  Fires a PropertyChangeEvent in response to a change in a bound property. The event will be delivered to all registered PropertyChangeListeners. No event will be delivered if oldValue and newValue are the same.