Java Code

                    KeyFrame fadeOutKey1 = new KeyFrame(Duration.millis(500), new KeyValue (toastStage.getScene.getRoot.opacityProperty, 0));

                    tl2.getKeyFrames.add(fadeOutKey1);   

                    tl2.setOnFinished((aeb) -> toastStage.close);

                    tl2.play;

            }).start;

        });

        tl1.play;

    }

Генератор арифметического примера

 String arithSchema1{

        int a,b,c,d;

        Random random=new Random;