Tugas 7 PBO Login (Pemrograman GUI)

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Login {
    String Username = "elonmusk";
    String Password = "69420";
    String msg = " ";
    private JTextField txtUsername;
    private JPasswordField txtPassword;
    public static void main (String args[]){
        Login gui = new Login();
        gui.go();
    }

    public void go() {
        JFrame frame = new JFrame("Welkom bij deze applicatie!");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        JLabel lblUsername = new JLabel("Gebruikersnaam ");
        JLabel lblPassword = new JLabel("Wachtwoord ");
        txtUsername = new JTextField(20);
        txtPassword = new JPasswordField(20);

        JButton btnLogin = new JButton("Inloggen");
        btnLogin.addActionListener(new LoginListener());
        JButton btnCancel = new JButton("Duidelijke Velden");
        btnCancel.addActionListener(new CancelListener());

        panel.add(lblUsername);
        panel.add(txtUsername);
        panel.add(lblPassword);
        panel.add(txtPassword);
        panel.add(btnLogin);
        panel.add(btnCancel);

        frame.getContentPane().add(BorderLayout.CENTER, panel);
        frame.setSize(300,300);
        frame.setVisible(true);
    }

    public class LoginListener implements ActionListener{//implements = adalah

        @Override
        public void actionPerformed(ActionEvent e) {
            if(Username.equals(txtUsername.getText())){
                if(Password.equals(txtPassword.getText())){
                    msg = "Toegang Verleend!";
                }else{
                    msg = "Toegang Geweigerd!";
                }
            }else{
                msg = "Toegang Geweigerd!";
            }
            JOptionPane.showMessageDialog(null,msg);
        }
    }

    public class CancelListener implements ActionListener{
        public void actionPerformed(ActionEvent e){
            txtUsername.setText("");
            txtPassword.setText("");
            txtUsername.requestFocus();
        }
    }
}

2. State awal program