Swing transparent form implementation

When I answered a question in the forum today, a netizen asked a question about how swing achieves window transparency. Third-party jna is required here. Jna-3.3.0-platform.jar package download: Click to open the link nonsense first less said, the first code posted out:

import java.awt.Color;  import java.awt.GradientPaint;  import java.awt.Graphics;  import java.awt.Graphics2D;    import javax.swing.JFrame;  import javax.swing.JPanel;    import com.sun.jna.platform.WindowUtils;      public class JFrameBackground {        public static void main(String[] args) {          JFrame frame = new JFrame();            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);            frame.setBounds(500, 500, 300, 300);            System.setProperty("sun.java2d.noddraw","true");          WindowUtils.setWindowAlpha(frame, 0.5f);          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);        }  }