如何将带有2DGraphics的JPanel放在JFrame上(同一个类)

import javax.swing.*;
import java.awt.*;

class MyPanel extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        // 在这里使用Graphics对象g进行2D绘图操作
    }
}

class MyFrame extends JFrame {
    public MyFrame() {
        setTitle("2D Graphics Demo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500, 500);
        setLocationRelativeTo(null);
        setResizable(false);
        
        // 创建一个MyPanel对象，并将其添加到JFrame中
        MyPanel panel = new MyPanel();
        getContentPane().add(panel);
    }
}

public class Main {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                MyFrame frame = new MyFrame();
                frame.setVisible(true);
            }
        });
    }
}