Créer une boîte de message JavaFX

// write your package name
package com.mycompany.javafx_messagebox;

// import required libraries
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.layout.TilePane;
import javafx.stage.Stage;

/**
 * JavaFX App
 */
public class App extends Application {
  @Override
  public void start(Stage stage) {
    // create a tile pane
    TilePane r = new TilePane();
    // add padding
    r.setPadding(new Insets(10, 10, 10, 10));

    // an array of button names
    String[] buttonNames = {"Confirmation MessageBox", "Error MessageBox", "Information MessageBox",
        "Warning MessageBox"};

    // Show no alert at the startup of the program
    Alert alert = new Alert(AlertType.NONE);

    /*
    a loop to create buttons, define actions when
    they are pressed and add them to the tile pane
    */
    for (String s : buttonNames) {
      Button button = new Button(s);

      button.setOnAction((ActionEvent event) -> {
        if (null != button.getText()) {
          switch (button.getText()) {
            case "Confirmation MessageBox":
              // set alert type, title, content text and then show it
              alert.setAlertType(AlertType.CONFIRMATION);
              alert.setTitle("Confirmation MessageBox");
              alert.setContentText("This is a CONFIRMATION "
                  + "message for you!");
              alert.show();
              break;
            case "Error MessageBox":
              // set alert type, title, content text and then show it
              alert.setAlertType(AlertType.ERROR);
              alert.setTitle("Error MessageBox");
              alert.setContentText("This is an ERROR message for you!");
              alert.show();
              break;
            case "Information MessageBox":
              // set alert type, title, content text and then show it
              alert.setAlertType(AlertType.INFORMATION);
              alert.setTitle("Information MessageBox");
              alert.setContentText("This is a INFORMATION "
                  + "message for you!");
              alert.show();
              break;
            case "Warning MessageBox":
              // set alert type, title, content text and then show it
              alert.setAlertType(AlertType.WARNING);
              alert.setTitle("Warning MessageBox");
              alert.setContentText("This is a WARNING message for you!");
              alert.show();
              break;
            default:
              break;
          }
        }
      });

      // add button
      r.getChildren().add(button);
    }

    // create a scene
    Scene sc = new Scene(r, 640, 50);

    // set the scene
    stage.setScene(sc);

    // show the stage
    stage.show();

  } // end start method

  // main method
  public static void main(String[] args) {
    launch(args);
  } // end main

} // end App class