import java.awt.*;
import javax.swing.*;
class Panel extends JPanel {
public static void main(String[] args){
Panel panel = new Panel();
panel.go();
}
public void go(){
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(300,300);
frame.setVisible(true);
}
public void paintComponent(Graphics g){
g.setColor(Color.orange);
g.fillRect(20,50,100,100);
}
}
以上代码编译可以通过,但是执行出来的就一个空白frame,没有paintComponent(Graphics g){}里的图画内容,要怎么改