关于Java的applet程序，为什么无法初始化？有init函数的

代码如下：

 package QAppLet;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.awt.Button;
class Pannel extends Panel{
Pannel(String s){
    setLayout(new BorderLayout());
    add("Cdnter",new Button(s));
    add("East",new Button(s));
    add("West",new Button(s));
    add("South",new Button(s));
    add("North",new Button(s));
}
}
public class PanLayout extends Applet{
    Button first=new Button("first card"),second=new Button("second card"),
            third=new Button("third card");
    Panel Card=new Panel();
    CardLayout c1=new CardLayout();
    public void init(){
        setLayout(new BorderLayout());
        Panel p=new Panel();
        p.setLayout(new FlowLayout());
        p.add(first);
        p.add(second);
        p.add(third);
        add("North",p);
        Card.setLayout(c1);
        Card.add("card1",new Pannel("In the first card"));
        Card.add("card2", new Pannel("In the second card"));
        Card.add("card3", new Pannel("In the third card"));
        first.addActionListener(new ActionButton());
        second.addActionListener(new ActionButton());
        third.addActionListener(new ActionButton());
    }
class ActionButton implements ActionListener{
    public void actionPerformed(ActionEvent e){
        Object source=e.getSource();
        if(source==first){
            c1.first(Card);
        }
        else if(source==second){
            c1.first(Card);
            c1.next(Card);
        }
        else if(source==third){
            c1.last(Card);
        }
    }
}
}

没有主函数，当然不能初始化了，加一个public static void main(string[] arg){
// 调用你上面的方法
}
这样就可以了