private void init() {
   for (int i = 0; i < 10; i++) {
     final int digit = i;
     view.setDigitHandler(i, (e) -> model.typeDigit(digit));
   }
   view.setClearHandler((e) -> model.clear());
   view.setEqualHandler((e) -> model.calculate());
   view.setPlusHandler((e) -> model.apply(Op.PLUS));
   view.setMinusHandler((e) -> model.apply(Op.MINUS));
   view.setMultiplyHandler((e) -> model.apply(Op.MULTIPLY));
   view.setDivideHandler((e) -> model.apply(Op.DIVIDE));
   model
       .getValue()
       .addListener(
           (observable, oldValue, newValue) ->
               eventBus.post(new ValueChanged(newValue.doubleValue())));
 }
 public Region getView() {
   return view.getNode();
 }