1、編寫(xiě)applet程序1，在屏幕上畫(huà)一組同心圓，相鄰兩圓的直徑大小相差10(pixel)；

import java.applet.*;
import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;

public class AppletCircle extends Applet {
public void init() {
   this.setSize(400, 400);
}

public void paint(Graphics g) {
   Color color ;
   for (int i=0; i<20; i++){
    color = new Color((int)(Math.random()*256),(int)(Math.random()*256),(int)(Math.random()*256));
    g.setColor(color);
    g.drawOval(20+5*i, 30+5*i, 300-10*i, 300-10*i);
   }
}

public static void main(String[] args){
   new AppletCircle();
}
}