济南历下学区:我用java编了一个,但系统提示有错(程序源码及错误码提示如下),请高手帮忙~!

程序源码为:
import java.awt.Graphics;
import java.applet.Applet;
import java.awt.Color;
class circle
{
protected int x,y,width,height;
circle (int a,int b,int c,int d)
{
x=a;
y=b;
width=c;
height=d;
}
}
public class showcircle2 extends Applet
{
circle t;
public void paint (Graphics g)
{
t=new circle (35,35,50,100);
g.setColor(Color.red);
g.fillOval(t.x,t.y,t.width,t.height);
t=new circle(70,70,20,30);
g.setColor(Color.blue);
g.fillOval(t.x,t.y,t.width,t.height);
}
}
提错内容:"WARNING: Default charset GBK not suppported,using ISO-8859-1 intstead
Exception in thread "main" java.lang.NoSuchMethod Error:main"
谢谢各位仁兄提示`~~但是我用Appletviewer运行后,系统再次提示发错,内容为: " 进行读取时出现I/O异常: E:\j2sdk1.4\javacode\showcircle2(系统找不到指定的文件.)" 请仁兄不吝赐教~~