How to use : Java GUI Create Tab and Multiple Tab Item

package com.java.myapp;

import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;


public class MyForm extends JFrame {

	private	JPanel	panel1;
	private	JPanel	panel2;
	private	JPanel	panel3;
	private	JPanel	panel4;
	
	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				MyForm frame = new MyForm();
				frame.setVisible(true);
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public MyForm() {
		
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 458, 287);
		setTitle("ThaiCreate.Com Java GUI Tutorial");
		
		JPanel mainPanel = new JPanel();
		mainPanel.setLayout(new BorderLayout());
		getContentPane().add(mainPanel);
		
		itemTabPanel1();
		itemTabPanel2();
		itemTabPanel3();
		itemTabPanel4();

		JTabbedPane tabPane = new JTabbedPane();
		tabPane.addTab( "Tab 1", panel1);
		tabPane.addTab( "Tab 2", panel2);
		tabPane.addTab( "Tab 3", panel3);
		tabPane.addTab( "Tab 4", panel4);
		mainPanel.add(tabPane);

	}
	
	public void itemTabPanel1()
	{
		panel1 = new JPanel();
		panel1.setLayout(null);
		
		JButton btn1 = new JButton("Button 1");
		btn1.setBounds(10, 11, 89, 23);
		panel1.add(btn1);
		
		JButton btn2 = new JButton("Button 2");
		btn2.setBounds(10, 45, 89, 23);
		panel1.add(btn2);
	}

	public void itemTabPanel2()
	{
		panel2 = new JPanel();
		panel2.setLayout(null);
		
		JButton btn3 = new JButton("Button 3");
		btn3.setBounds(10, 11, 89, 23);
		panel2.add(btn3);
		
		JButton btn4 = new JButton("Button 4");
		btn4.setBounds(10, 45, 89, 23);
		panel2.add(btn4);	
	}

	public void itemTabPanel3()
	{
		panel3 = new JPanel();
		panel3.setLayout(null);;
		
		JButton btn5 = new JButton("Button 5");
		btn5.setBounds(10, 11, 89, 23);
		panel3.add(btn5);
		
		JButton btn6 = new JButton("Button 6");
		btn6.setBounds(10, 45, 89, 23);
		panel3.add(btn6);		
		
	}
	
	public void itemTabPanel4()
	{
		panel4 = new JPanel();
		panel4.setLayout(null);;
		
		JButton btn7 = new JButton("Button 7");
		btn7.setBounds(10, 11, 89, 23);
		panel4.add(btn7);
		
		JButton btn8 = new JButton("Button 8");
		btn8.setBounds(10, 45, 89, 23);
		panel4.add(btn8);	
	}
}