Sample to check:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class App extends Application {

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

    @Override
    public void start(Stage stage) throws Exception {
        MenuBar control = new MenuBar();
        for (int i = 0; i < 5; i++) {
            Menu m = new Menu("Menu _" + String.valueOf(i + 1));
            m.setMnemonicParsing(true);
            for (int j = 0; j < 5; j++) {
                Menu s = new Menu("Submenu _" + String.valueOf(j + 1));
                s.setMnemonicParsing(true);
                for (int k = 0; k < 5; k++) {
                    MenuItem item = new MenuItem("Item _" + String.valueOf(k + 1));
                    item.setMnemonicParsing(true);
                    s.getItems().add(item);
                }
                m.getItems().add(s);
            }
            control.getMenus().add(m);
        }
        Scene scene = new Scene(new HBox(control));
        stage.setScene(scene);
        stage.show();
    }
}