import java.applet.Applet;                                 
import java.awt.Button;                                    
import java.awt.Color;                                      
import java.awt.Graphics;                                   
public class TestApp extends Applet{                        
    Button bt;                                             
     void Applet()                                          
    {                                                      
        bt=new Button("确定");                                
        bt.setBackground(Color.BLUE);                       
        add(bt);                                            
    }                                                      
    public void paint(Graphics g)                           
    {                                                      
        g.drawString("调用add方法在容器中添加按钮", 20, 80);            
    }                                                      
    public void init()                                      
    {                                                      
        Applet smp=new Applet();                           
    }                                                      
}                                                           
为什么运行之后没有按钮