Swing界面透明设置方法

import com.sun.awt.AWTUtilities;import java.awt.Color;import java.awt.Graphics;import javax.swing.JFrame;import javax.swing.JPanel;public class Test {    public static void main(String[] args) {        JFrame frame = new JFrame();        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        frame.setUndecorated(true);        frame.setBounds(500, 500, 300, 300);        AWTUtilities.setWindowOpaque(frame, false);        JPanel pane = new JPanel() {            @Override            public void paint(Graphics g) {                super.paint(g);                g.setColor(Color.red);                g.fill3DRect(10, 10, 100, 100, true);            }        };        frame.setContentPane(pane);        frame.setVisible(true);    }}