protected static boolean showSecondStageFlag = false;
    protected static Stage stage;

    @FXML
    private void newStageButtonAction(ActionEvent event) {
        CreateSecondStage cs = new CreateSecondStage();
        cs.start();
    }

    public class CreateSecondStage
        extends Thread {

         @Override
        public void run() {

                Platform.runLater(new Runnable() {
                    @Override
                    public void run() { createStage(); }
                });

            int x = 1;

                while(!showSecondStageFlag) {
                    final int y = x;
                        Platform.runLater(new Runnable() {
                            @Override
                            public void run() { label.setText(String.valueOf(y)); }
                        });
                        try { TimeUnit.SECONDS.sleep(1);
                        } catch (InterruptedException ex) { Logger.getLogger(ThreadsFXTestFXMLController.class.getName()).log(Level.SEVERE,null,ex); }
                    x++;
                }

        }

        void createStage() {
            try {
                stage = new Stage();
                Parent root = FXMLLoader.load(getClass().getResource("SecondStage.fxml"));
                Scene scene = new Scene(root);
                stage.setScene(scene);
            } catch (IOException ex) { Logger.getLogger(ThreadsFXTestFXMLController.class.getName()).log(Level.SEVERE,null,ex); }
        }

    }

    @Override
    public void initialize(URL url,ResourceBundle rb) {
        SecondStageThread st = new SecondStageThread();
        st.start();
    }

    public class SecondStageThread
                extends Thread {

        @Override
        public void run() {
                for(int x=0;x<10;x++) {
                    try { TimeUnit.SECONDS.sleep(1);
                    } catch (InterruptedException ex) { Logger.getLogger(ThreadsFXTestFXMLController.class.getName()).log(Level.SEVERE,null,ex); }
                }

            ThreadsFXTestFXMLController.showSecondStageFlag = true;

                Platform.runLater(new Runnable() {
                    @Override
                    public void run() { ThreadsFXTestFXMLController.stage.show(); }
                });

        }

    }

        Task t = new Task() {
            @Override
            protected Object call() throws Exception {
                    for(int x=0;x<=10;x++) {
                            if(isCancelled()) {
                                updateMessage("isCancelled");
                                break;
                            }
                        TimeUnit.MILLISECONDS.sleep(100);
                    }
                return null;
            }
        };
        new Thread(t).start();
        button.setOnMouseClicked(new EventHandler<MouseEvent>(){
            @Override
            public void handle(MouseEvent event) {
                t.cancel();
            }
        });

try {
     TimeUnit.MILLISECONDS.sleep(800);
}catch(InterruptedException ex) {
     if(isCancelled()) {
           updateMessage("isCancelled");
           break;
     }
}

                        if(x%3==0){
                            updateMessage(String.valueOf(x));
                            System.out.println(x + " " + msg);
                            cancel();
                        }

    private class MyScheduledService
                extends ScheduledService<Void> {

        int period,x=1;
        String msg = "working";

        MyScheduledService(int _period) {
            this.period = _period;
        }

        @Override
        protected Task<Void> createTask() {
            return new Task(){
                @Override
                protected Void call() throws Exception {
                    setPeriod(Duration.millis(period));
                    setDelay(Duration.millis(period));
                        if(isCancelled()) {
                            updateMessage("Cancel");
                            System.out.println("Cancel");
                        }
                    updateMessage(String.valueOf(x));
                    System.out.println(x + " - " + msg);
                    x++;
                    return null;
                }
            };
        }

btnStart.setOnAction((ActionEvent t) -> { ss.start(); });