为什么这个tabbedpane 不显示出来呀？

请大家帮我看看下面的程序出了什么问题？我是想创建一个tabbedpane,结果程序运行之后什么也没有显示出来，不知道为什么？大部分code都是系统自动生成的，我就写了几行code,方便大家看，我把我写的code用红色标示出来,多谢了!package jTabbedPaneDemo;
import javax.swing.*;
import java.awt.*;
/**
 *
 * @author violetc
 */
public class TopPannel extends javax.swing.JPanel {    /** Creates new form TopPannel */
    public TopPannel() {
        initComponents();
        this.setVisible(true);    }    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {        jTabbedPane1 = new javax.swing.JTabbedPane();
        jPanel2 = new javax.swing.JPanel();
        jPanel3 = new javax.swing.JPanel();
        jPanel1 = new javax.swing.JPanel();
        FirstNamejTextField = new javax.swing.JTextField();
        FirstName = new javax.swing.JLabel();
        LastName = new javax.swing.JLabel();
        LastNamejPasswordField = new javax.swing.JPasswordField();        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 397, Short.MAX_VALUE)
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 250, Short.MAX_VALUE)
        );        jTabbedPane1.addTab("tab2", jPanel2);        javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
        jPanel3.setLayout(jPanel3Layout);
        jPanel3Layout.setHorizontalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 397, Short.MAX_VALUE)
        );
        jPanel3Layout.setVerticalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 250, Short.MAX_VALUE)
        );        jTabbedPane1.addTab("tab3", jPanel3);        FirstName.setText("First Name");        LastName.setText("Last Name");        LastNamejPasswordField.setText("jPasswordField1");        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(59, 59, 59)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(LastName, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(FirstName, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(FirstNamejTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 118, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(LastNamejPasswordField, javax.swing.GroupLayout.PREFERRED_SIZE, 119, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(138, 138, 138))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(50, 50, 50)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(FirstNamejTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(FirstName, javax.swing.GroupLayout.PREFERRED_SIZE, 18, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(LastName, javax.swing.GroupLayout.PREFERRED_SIZE, 18, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(LastNamejPasswordField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(154, Short.MAX_VALUE))
        );        jTabbedPane1.addTab("tab1", jPanel1);        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jTabbedPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 402, Short.MAX_VALUE)
                .addGap(20, 20, 20))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jTabbedPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 278, Short.MAX_VALUE)
                .addGap(22, 22, 22))
        );
    }// </editor-fold>
    // Variables declaration - do not modify
    private javax.swing.JLabel FirstName;
    private javax.swing.JTextField FirstNamejTextField;
    private javax.swing.JLabel LastName;
    private javax.swing.JPasswordField LastNamejPasswordField;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JTabbedPane jTabbedPane1;
    // End of variables declaration public static void main(String[] args){
 SwingUtilities.invokeLater(new RunnableDemo());
 } private static class RunnableDemo implements Runnable {        public RunnableDemo() {
        }        public void run() {
            new TopPannel();
        }
    }
}