为什么我的tabbedPane显不出来?

在tabbedPanel类的构造函数中，应该加入
this.add(tabPanel);
没有显示是因为根本就没有加入到tabbedPanel中。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class tabbedPanel extends JPanel{
private JTabbedPane tabPanel;
public tabbedPanel(){
tabPanel=new JTabbedPane();
JPanel p2=new JPanel();
tabPanel.addTab("two",null,p2,"2");
tabPanel.setSelectedIndex(0);
this.add(tabPanel); //要把组件添加到容器里！
}
}
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class t extends JFrame{
tabbedPanel tab=new tabbedPanel();
t(){
add(tab);
setSize(500,500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
public static void main(String[]args){
t t1=new t();
}
}