Java JFrame mix heavyweight and lightweight components

import java.awt.Button;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;

public class Main extends JFrame {

   public Main() {
      this.setTitle("Example");
      this.setSize(200, 100);
      this.setLocationRelativeTo(null);
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      this.setLayout(new FlowLayout());

      Button exitButton = new Button("Exit");
      exitButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event) {
            System.exit(0);/*www . j  a v a2 s. c om*/
         }
      });
      this.add(exitButton);

      JMenuBar menuBar = new JMenuBar();
      JMenu menu = new JMenu("Overlapping Menu");
      JMenuItem menuItem = new JMenuItem("Overlapping Item");
      menu.add(menuItem);
      menuBar.add(menu);
      this.setJMenuBar(menuBar);
      this.validate();
   }
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         @Override
         public void run() {
            Main window = new Main();
            window.setVisible(true);
         }
      });
   }
}