import javax.swing.JFrame;
public class MyMoonFrame {
 public static void main(String[] args) {
  JFrame frame= new JFrame();
  frame.setSize(1024,768);
  frame.setLocation(100,100);
  MyMoonPanel panel=new MyMoonPanel();
  frame.add(panel);
  panel.startRun();
  frame.setVisible(true);
 }
}

package day3;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class MyMoonPanel extends JPanel{
 int x=700;
 public void startRun(){
  new Thread(){
   public void run(){
    while(true){
     //让要去覆盖月亮的黑圆的横坐标坐标不断自增 
     //这样去接近月亮和远离，造成月亮变化的效果 
     for (int i=0;i<1024;i++){
      x++;
      if(x>1024){
       x=0;
      }
     }
     try {
      //让线程休眠10毫秒 
      Thread.sleep(10);
     }
     catch (InterruptedException e) {
      // TODO Auto-generated catch block 
      e.printStackTrace();
     }
     //刷新屏幕，自动调用paint()方法 
     repaint();
    }
   }
  }
  .start();
 }
 public void paint(Graphics g){
  super.paint(g);
  //设置背景 
  this.setBackground(Color.black);
  //月亮 
  g.setColor(Color.yellow);
  g.fillArc(500, 100, 200, 200, 0, 360);
  //设置将去覆盖月亮的黑色圆 
  g.setColor(Color.black);
  g.fillArc(x, 100, 200, 200, 0, 360);
 }
}