Swing写一个鼠标点击哪里就会画出一个圆

package demo03;

import java.awt.EventQueue;
import java.awt.Graphics;

import javax.swing.JFrame;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JPanel;
import java.awt.BorderLayout;

public class Mouse02 {

    private JFrame frame;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Mouse02 window = new Mouse02();