protected void notifyPropertyChangeListener(String property,Object oldValue,Object newValue){
  Set<PropertyChangeListener> v;
synchronized (this) {
    v=new HashSet<>(listeners);
  }
  for (  PropertyChangeListener listener : v) {
    listener.propertyChange(new PropertyChangeEvent(this,property,oldValue,newValue));
  }
}

protected void notifyPropertyChangeListener ( String property , Object oldValue , Object newValue ) { Set < PropertyChangeListener > v ; synchronized ( this ) { v = new HashSet < > ( listeners ) ; } for ( PropertyChangeListener listener : v ) { listener . propertyChange ( new PropertyChangeEvent ( this , property , oldValue , newValue ) ) ; } }
trigger the notification of all propertychangelisteners
