Panel in the Frame，手动居中

import java.awt.*;public class TestCenterPanel {public static void main(String[] args) {new SelfFrame("FrameWithPanel", 50,50,400,400);}}class SelfFrame extends Frame{private Panel pn;SelfFrame(String str, int x, int y, int width, int height){super(str);super.setBackground(Color.blue);super.setVisible(true);super.setBounds(x, y, width, height);super.setLayout(null);pn = new Panel(null);pn.setBackground(Color.yellow);pn.setBounds((width-width/2)/2, (height-height/2)/2, width/2, height/2);super.add(pn);}}