How to use : Java GUI Create Menu and Open Another Panel Layout

PanelFrame panel = new PanelFrame();
panel.setBorder(BorderFactory.createTitledBorder("Panel"));
getContentPane().removeAll();
getContentPane().add(panel, BorderLayout.CENTER);
getContentPane().doLayout();

package com.java.myapp;

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;

public class MyForm extends JFrame {

	static JPanel MainPanel;
	/**
	 * 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, 508, 375);
		setTitle("ThaiCreate.Com Java GUI Tutorial");
		
		getContentPane().add(new PanelMain()); // Load Panel Main
		
		// Menu Bar
        JMenuBar menuBar=new JMenuBar();
        
        // Main Menu
        JMenu menuMain = new JMenu("File");
        
        // Panel 1
        JMenuItem menu1 = new JMenuItem("Menu 1 - Panel 1");
        menu1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
            	PanelFrame1 panel1 = new PanelFrame1();
            	panel1.setBorder(BorderFactory.createTitledBorder("Panel 1"));
                getContentPane().removeAll();
                getContentPane().add(panel1, BorderLayout.CENTER);
                getContentPane().doLayout();
            }
        });
        
        // Panel 2
        JMenuItem menu2 = new JMenuItem("Menu 2 - Panel 2");
        menu2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
            	PanelFrame2 panel2 = new PanelFrame2();
            	panel2.setBorder(BorderFactory.createTitledBorder("Panel 2"));
                getContentPane().removeAll();
                getContentPane().add(panel2, BorderLayout.CENTER);
                getContentPane().doLayout();
            }
        });
        
        // Class 3
        JMenuItem menu3 = new JMenuItem("Menu 3 - Panel 3");
        menu3.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
            	PanelFrame3 panel3 = new PanelFrame3();
            	panel3.setBorder(BorderFactory.createTitledBorder("Panel 3"));
                getContentPane().removeAll();
                getContentPane().add(panel3, BorderLayout.CENTER);
                getContentPane().doLayout();
            }
        });
        
        menuMain.add(menu1);
        menuMain.add(menu2);
        menuMain.add(menu3);
        menuBar.add(menuMain);

        
        setJMenuBar(menuBar);
	}
	

}

package com.java.myapp;

import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import java.awt.Font;

public class PanelMain extends JPanel {

	/**
	 * Create the panel.
	 */
	public PanelMain() {
		setLayout(null);
		
		JLabel lblPanelMain = new JLabel("Panel Main");
		lblPanelMain.setFont(new Font("Tahoma", Font.PLAIN, 20));
		lblPanelMain.setHorizontalAlignment(SwingConstants.CENTER);
		lblPanelMain.setBounds(105, 110, 239, 31);
		add(lblPanelMain);

	}
}

package com.java.myapp;

import javax.swing.JPanel;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.SwingConstants;
import javax.swing.JButton;
import javax.swing.JSpinner;
import javax.swing.JFormattedTextField;

public class PanelFrame1 extends JPanel {

	/**
	 * Create the panel.
	 */
	public PanelFrame1() {
		setLayout(null);
		
		JLabel label = new JLabel("Panel 1");
		label.setHorizontalAlignment(SwingConstants.CENTER);
		label.setFont(new Font("Tahoma", Font.PLAIN, 20));
		label.setBounds(108, 33, 239, 31);
		add(label);
		
		JButton btnNewButton = new JButton("New button");
		btnNewButton.setBounds(70, 99, 89, 23);
		add(btnNewButton);
		
		JLabel lblNewLabel = new JLabel("New label");
		lblNewLabel.setBounds(113, 154, 46, 14);
		add(lblNewLabel);
		
		JSpinner spinner = new JSpinner();
		spinner.setBounds(281, 100, 29, 20);
		add(spinner);
		
		JFormattedTextField formattedTextField = new JFormattedTextField();
		formattedTextField.setBounds(193, 217, 141, 20);
		add(formattedTextField);

	}
}

package com.java.myapp;

import javax.swing.JPanel;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.SwingConstants;
import javax.swing.JEditorPane;
import javax.swing.JToggleButton;
import javax.swing.JComboBox;
import javax.swing.JButton;

public class PanelFrame2 extends JPanel {

	/**
	 * Create the panel.
	 */
	public PanelFrame2() {
		setLayout(null);
		
		JLabel label = new JLabel("Panel 2");
		label.setHorizontalAlignment(SwingConstants.CENTER);
		label.setFont(new Font("Tahoma", Font.PLAIN, 20));
		label.setBounds(108, 42, 239, 31);
		add(label);
		
		JEditorPane editorPane = new JEditorPane();
		editorPane.setBounds(10, 111, 106, 20);
		add(editorPane);
		
		JToggleButton tglbtnNewToggleButton = new JToggleButton("New toggle button");
		tglbtnNewToggleButton.setBounds(135, 111, 121, 23);
		add(tglbtnNewToggleButton);
		
		JComboBox comboBox = new JComboBox();
		comboBox.setBounds(155, 168, 28, 20);
		add(comboBox);
		
		JButton btnNewButton = new JButton("New button");
		btnNewButton.setBounds(275, 190, 89, 23);
		add(btnNewButton);
		
		JButton btnNewButton_1 = new JButton("New button");
		btnNewButton_1.setBounds(47, 208, 89, 23);
		add(btnNewButton_1);

	}
}

package com.java.myapp;

import javax.swing.JPanel;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.SwingConstants;
import javax.swing.JButton;

public class PanelFrame3 extends JPanel {

	/**
	 * Create the panel.
	 */
	public PanelFrame3() {
		setLayout(null);
		
		JLabel label = new JLabel("Panel 3");
		label.setHorizontalAlignment(SwingConstants.CENTER);
		label.setFont(new Font("Tahoma", Font.PLAIN, 20));
		label.setBounds(111, 43, 239, 31);
		add(label);
		
		JButton btnNewButton = new JButton("New button");
		btnNewButton.setBounds(127, 136, 89, 23);
		add(btnNewButton);
		
		JButton btnNewButton_1 = new JButton("New button");
		btnNewButton_1.setBounds(288, 198, 89, 23);
		add(btnNewButton_1);
		
		JButton btnNewButton_2 = new JButton("New button");
		btnNewButton_2.setBounds(56, 198, 89, 23);
		add(btnNewButton_2);

	}

}