HelloWorld with JavaFX

Here is the HelloWorld JavaFX application that shows the Hello, World! and Exit text:

import javafx.application.Application;

import javafx.application.Platform;

import javafx.scene.control.Button;

import javafx.scene.layout.Pane;

import javafx.scene.text.Text;

import javafx.scene.Scene;

import javafx.stage.Stage;

public class HelloWorld extends Application {

  public static void main(String... args) {

      launch(args);

  }

  @Override

  public void start(Stage primaryStage) {

    Text txt = new Text("Hello, world!");

    txt.relocate(135, 40);

    Button btn = new Button("Exit");

    btn.relocate(155, 80);

    btn.setOnAction(e:> {

        System.out.println("Bye! See...