JavaFX RadioMenuItem create and add to menu

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.control.RadioMenuItem;
import javafx.scene.control.SeparatorMenuItem;
import javafx.scene.control.ToggleGroup;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class Main extends Application {
  //Create a label that will report the selection.
  private Label response = new Label("Menu Demo");

  public static void main(String[] args) {
    launch(args);/* www. j  av  a  2  s.  c  om*/
  }
  public void start(Stage myStage) {    myStage.setTitle("Menus from java2s.com");

    // Use a BorderPane for the root node.
    BorderPane rootNode = new BorderPane();

    Scene myScene = new Scene(rootNode, 300, 300);

    myStage.setScene(myScene);

    // Create the menu bar.
    MenuBar mb = new MenuBar();

    // Create the File menu, including a mnemonic.
    Menu fileMenu = new Menu("_File");
    MenuItem open = new MenuItem("Open");
    MenuItem close = new MenuItem("Close");
    MenuItem save = new MenuItem("Save");
    MenuItem exit = new MenuItem("Exit");
    
    // Create the Priority sub menu.
    Menu priorityMenu = new Menu("Priority");

    // Use radio menu items for the priority setting.
    RadioMenuItem high = new RadioMenuItem("High");
    RadioMenuItem low = new RadioMenuItem("Low");
    priorityMenu.getItems().addAll(high, low);
    // Create a toggle group and use it for the radio menu items.
    ToggleGroup tg = new ToggleGroup();
    high.setToggleGroup(tg);
    low.setToggleGroup(tg);

    // Select High priority for the default selection.
    high.setSelected(true);

    
    fileMenu.getItems().addAll(priorityMenu,open, close, save, new SeparatorMenuItem(), exit);

    // Add File menu to the menu bar.
    mb.getMenus().add(fileMenu);

    // the response label to the center position.
    rootNode.setTop(mb);
    rootNode.setCenter(response);

    myStage.show();
  }
}