question: public void removePropertyChangeListener ( String propertyName , PropertyChangeListener listener ) { if ( listener != null ) { synchronized ( this ) { if ( changeSupport != null ) { changeSupport . removePropertyChangeListener ( propertyName , listener ) ; } } } }
target:  Removes a PropertyChangeListener from the listener list for a specific property. This method should be used to remove PropertyChangeListeners that were registered for a specific bound property. <p> If listener is null, no exception is thrown and no action is performed.