Java小程序问题！求解答！

class ButtonPanel extends Panel
{
    ButtonPanel(String id)
    {
        setLayout(new BorderLayout());
        add("Center",new Button(id));
    }
   
}
public class Hello extends Applet
{
    Button
        first = new Button("first"),
        second = new Button("second"),
        third = new Button("third");
    Panel cards = new Panel();
    Panel p = new Panel();
    CardLayout c1 = new CardLayout();        
    public void init()
    {
        setLayout(new CardLayout());
        p.setLayout(new FlowLayout());
        p.add(first);
        p.add(second);
        p.add(third);
        cards.setLayout(c1);
  //这三句cards都没有弹出，应该有反应才对啊！为什么n呢？求解，谢谢！
        cards.add("first card",new ButtonPanel("the first one"));           
        cards.add("second card",new ButtonPanel("the second one"));
        cards.add("third card",new ButtonPanel("the third one"));
        add("North",p);
        add("Center",cards);   
    }   
    public boolean action(Event evt,Object arg)
    {
        if(evt.target.equals(first))
            c1.first(cards);
        else if(evt.target.equals(second))
        {
            c1.first(cards);
            c1.next(cards);
        }
        else if(evt.target.equals(third))
            c1.last(cards);
        else
            return super.action(evt, arg);
        return true;
    }
}

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