Javaアプリの背景を透明にする方法は？

import java.awt.AWTException;
import java.awt.Button;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;

public class TransFrame extends Frame {
    private Robot robot; 
    private BufferedImage backImage;
    private int x;
    private int y;
    private int width;
    private int height;

    public TransFrame(int x, int y, int width, int height) {
        setUndecorated(true);
        setBounds(x, y, width, height);
        setLayout(new FlowLayout());

        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;

        try {
            robot = new Robot();
        } catch (AWTException ex) {
            ex.printStackTrace();
            return;
        }


        Button recaptureButton = new Button("Recapture");
        recaptureButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent event) {
                    copyScreen();
                }
            });
        add(recaptureButton);

        Button closeButton = new Button("Close");
        closeButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent event) {
                    System.exit(0);
                }
            });

        add(closeButton);

        copyScreen();
    }

    public void paint(Graphics g) {
        g.drawImage(backImage, 0, 0, this);
    }

    private synchronized void copyScreen() {
            hide();
            try {
                Thread.sleep(100L);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            }

            backImage = robot.createScreenCapture(new Rectangle(x, y, width, height));
            show();
    }

    public static void main(String[] args) {
        int x = Integer.parseInt(args[0]);
        int y = Integer.parseInt(args[1]);
        int width = Integer.parseInt(args[2]);
        int height = Integer.parseInt(args[3]);
        
        new TransFrame(x, y, width, height).setVisible(true);
    }
}