public void fireOperatorMoved(Operator operator){
  List<Operator> list=new LinkedList<>();
  list.add(operator);
  fireOperatorsMoved(list);
}

public void fireOperatorMoved ( Operator operator ) { List < Operator > list = new LinkedList < > ( ) ; list . add ( operator ) ; fireOperatorsMoved ( list ) ; }
fire when an operator has been moved .
