请高手指点，哪儿有问题？谢谢！
import java.awt.Container;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;


/*
 * 应用程序有两个JPanel子类对象和一个按钮，每个JPanel子类
 * 对象又有两个按钮和一个标签。*/
public class Test6 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        JFrame f=new JFrame("MyWindow");
        MyJPanel p1=new MyJPanel("确定","取消","标签，我在面板1中");
        MyJPanel p2=new MyJPanel("确定","取消","标签，我在面板2中");
        JButton b3=new JButton("我是不在面板中的按钮");
        f.setSize(500,600);
        Container con=f.getContentPane();
        con.setLayout(new GridLayout(3,1));
        con.add(p1);
        con.add(p2);
        con.add(b3);
        f.setVisible(true);      
    }
}
class MyJPanel extends JPanel{
    MyJPanel(String str1,String str2,String str3){
        super();   
        JPanel p1=new JPanel();
        JButton b1=new JButton(str1);
        JButton b2=new JButton(str2);
        JLabel l1=new JLabel(str3);
        p1.add(b1);
        p1.add(b2);
        p1.add(l1);
        p1.setSize(50,150);
    }
}