如何在JPanel上绘制矩形？

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

public class MyPanel extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawRect(50, 50, 100, 50); // 绘制一个矩形，起始点坐标为(50, 50)，宽度为100，高度为50
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        MyPanel panel = new MyPanel();
        frame.add(panel);

        frame.setVisible(true);
    }
}