如何在JFrame内部的JPanel中绘制形状

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

public class ShapePanel extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        
        // 绘制矩形
        g.drawRect(50, 50, 100, 100);
        
        // 绘制椭圆
        g.drawOval(200, 50, 100, 100);
        
        // 绘制其他形状...
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Shape Panel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(null);

        ShapePanel shapePanel = new ShapePanel();
        shapePanel.setBounds(0, 0, 400, 300);
        shapePanel.setBackground(Color.WHITE);

        frame.add(shapePanel);
        frame.setSize(400, 300);
        frame.setVisible(true);
    }
}