如何使用图形在JPanel上绘图

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

public class MyPanel extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        
        // 绘制图形
        g.drawLine(50, 50, 200, 200); // 绘制一条线段
        g.drawRect(100, 100, 150, 100); // 绘制一个矩形
        g.drawOval(250, 250, 100, 100); // 绘制一个圆形
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("绘制图形示例");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        MyPanel panel = new MyPanel();
        frame.add(panel);
        
        frame.setSize(400, 400);
        frame.setVisible(true);
    }
}