Contoh listing java dalam pembuatan menu

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class menu extends JFrame implements ActionListener {
transpose tra;
determinan det;
JLabel label1= new JLabel("MENU");
JLabel label2= new JLabel("1. Transpose");
JLabel label3= new JLabel("2. Determinan");
JLabel label4= new JLabel("3. exit");
JLabel label5= new JLabel("pilih");
JTextField pilihan = new JTextField();
JButton ok=new JButton("ok");
JPanel panel =new JPanel();
public menu() {
setTitle("Menu");
setSize(300,200);
setLocationRelativeTo(null);
label1.setBounds(this.getWidth()/6,10,100,20);
label2.setBounds(50, 30, 100, 20);
label3.setBounds(50, 55, 100, 20);
label4.setBounds(50, 75, 100, 20);
label5.setBounds(20, 100, 50, 20);
pilihan.setBounds(50,100 ,100, 20);
ok.setBounds(160, 100, 50, 20);
ok.addActionListener(this);
panel.setLayout(null);
panel.add(label1);
panel.add(label2);
panel.add(label3);
panel.add(label4);
panel.add(label5);
panel.add(pilihan);
panel.add(ok);
getContentPane().add(panel); }
public void actionPerformed(ActionEvent e) {
if (e.getSource()==ok) {
int pil=Integer.parseInt(pilihan.getText());
switch(pil) {
case 1:tra=new transpose();
break;
case 2:det= new determinan();
break;
case 3:System.exit(0); } } }
public static void main(String [] args) {
menu tampilan=new menu();
tampilan.setVisible(true);
tampilan.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }