鼠标点一下出现一个点（不懂 ）

package cn.rushangw.lesson03;

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.Iterator;

//鼠标监听事件
public class TestMouseListener {
    public static void main(String[] args) {
        new MyFrame("画图");

    }
}

//鼠标类
class MyFrame extends Frame{
    //画画需要画笔,需要监听鼠标当前位置。需要集合来存储这个点
    ArrayList points;

    public MyFrame(String title)  {
        super(title);
        setBounds(200,200,400,300);
        setVisible(true);

        //存储鼠标点击的点
        points = new ArrayList();

        //鼠标监听器，针对窗口
        addMouseListener(new MyMouseListener());
    }

    @Override
    public void paint(Graphics g) {
        //画画，监听的鼠标事件
        Iterator iterator = points.iterator();
        while (iterator.hasNext()){
            Point point = (Point) iterator.next();
            g.setColor(Color.red);
            g.fillOval(point.x,point.y,10,10);
        }
    }
    //添加一个点到界面上
    public void addPaint(Point point){
        points.add(point);
    }
    //适配器模式
    private class MyMouseListener extends MouseAdapter {

        @Override
        public void mousePressed(MouseEvent e) {
            MyFrame frame = (MyFrame) e.getSource();
            //这个我们点击的时候，就会在界面上产生一个点！
            //这个点就是鼠标的点
            frame.addPaint(new Point(e.getX(),e.getY()));

            //每次点击鼠标都要重新画一遍
            frame.repaint();


        }
    }
}