problem in adding a fullscreen frame nd adding a glass pane to it

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class GlassPane {
  public static void main(String[] args) {
    JFrame f = new JFrame("GlassPane");

    final JPanel p1 = new JPanel();
    p1.add(new JLabel("GlassPane Example"));
    JButton show = new JButton("Show");
    p1.add(show);
    f.getContentPane().add(p1);

    final JPanel glass = (JPanel) f.getGlassPane();

    glass.setVisible(true);
    glass.setLayout(new GridBagLayout());
    JButton glassButton = new JButton("This is button in Glass Pane");
    glass.add(glassButton);

    f.setSize(250, 100);
    f.setVisible(true);

    boolean debug = false;
    if (debug) {
      System.out.println("Button is " + glassButton);
      System.out.println("GlassPane is " + glass);
    }
    show.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        glass.setVisible(true);
        p1.repaint();
      }
    });
      glassButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        glass.setVisible(false);
        p1.repaint();
      }
    });
  }
}