java基于GUI实现简单画笔小画板

this.addMouseListener(new MyMouseListener());

private class MyMouseListener extends MouseAdapter

@Override
    public void paint(Graphics g) {
        // paint listen on mouse event
        Iterator iterator = points.iterator();
        while (iterator.hasNext()){
            Point point = (Point) iterator.next();
            g.setColor(Color.GREEN);
            g.fillOval(point.x, point.y, 10, 10);
        }
    }

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

public class testmousepaint {
    public static void main(String[] args) {
        MyFrame myFrame = new MyFrame("IDEA");
    }
}

class MyFrame extends Frame{

    ArrayList points;

    public MyFrame(String title) {
        super(title);
        setBounds(200, 200, 400, 400);
        this.addMouseListener(new MyMouseListener());
        setVisible(true);
        setBounds(200,200,400,400);
        setBackground(Color.white);
        points = new ArrayList<>();
    }

    @Override
    public void paint(Graphics g) {
        // paint listen on mouse event
        Iterator iterator = points.iterator();
        while (iterator.hasNext()){
            Point point = (Point) iterator.next();
            g.setColor(Color.GREEN);
            g.fillOval(point.x, point.y, 10, 10);
        }
    }

    public void addpoint(Point point){
        points.add(point);
    }

    private class MyMouseListener extends MouseAdapter{
        @Override
        public void mousePressed(MouseEvent e) {
            MyFrame frame = (MyFrame) e.getSource();
            frame.addpoint(new Point(e.getX(), e.getY()));

            // click and paint every time
            frame.repaint();

        }
    }

}