I need help with my FullScreen Code

I am trying to get a simple fullscreen window for a game I am making. I have the code in my Screen class (With no apparent errors). I need to know how to run the fullscreen code from my FullScreenWindow class.

Here is the code for the Screen class:

Code :

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
 
import javax.swing.JFrame;
import javax.swing.JLabel;
 
@SuppressWarnings("serial")
public class Screen extends JFrame{
 
  public Screen( String title )
  {
      super(title);
 
      this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
 
      FullScreenWindow frame = new FullScreenWindow();
      frame.setVisible(true);
 
      GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
 
      setUndecorated(true);
      if (gd.isFullScreenSupported()) {
          setUndecorated(true);
          gd.setFullScreenWindow(this);
      } else {
          System.err.println("Full screen not supported");
          setSize(100, 100); // just something to let you see the window
          setVisible(true);
      }
      getContentPane().add(new JLabel("Test Fullscreen"), BorderLayout.NORTH);
      setBackground(Color.BLUE);
      setForeground(Color.WHITE);
      setFont(new Font("Arial", Font.PLAIN, 24));
      drawString("This is cool", 200, 200);
      if(isVisible() == true){
    	  try{
    		  try {
				Thread.sleep(5000);
			} catch (Exception ex) {
				ex.printStackTrace();
			}
    	  }finally{
    		  Screen.this.setVisible(false);
              System.exit(0);
    	  }
      }
  }
 
 
 
private void drawString(String string, int i, int j) {
	// TODO Auto-generated method stub
 
}
}

Here is the code in my FullScreenWindow class (my main class)

Code :

import java.awt.*;
import javax.swing.*;
@SuppressWarnings("serial")
public class FullScreenWindow extends JFrame {
}