head first java解决办法

package simpleAnimation;import javax.swing.*;import java.awt.*;public class SimpleAnimation{    int x=70;    int y=70;        public static void main(String[] args)    {        SimpleAnimation gui=new SimpleAnimation();        gui.go();    }    public void go()    {        JFrame frame=new JFrame();        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);                MyDrawPanel drawPanel=new MyDrawPanel();                frame.getContentPane().add(drawPanel);        frame.setSize(300,300);        frame.setVisible(true);                for(int i=0;i<130;i++)        {            x++;            y++;            drawPanel.repaint();                        try            {                Thread.sleep(50);            }            catch(Exception ex)            {}        }    }    class MyDrawPanel extends JPanel    {        public void paintComponet(Graphics g)        {            g.setColor(Color.white);            g.fillRect(0, 0, this.getWidth(), this.getHeight());            g.setColor(Color.green);            g.fillOval(x,y,40,40);        }    }}