[dúvida] Meu código naum funfa direito

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

class WindowLogin extends JFrame {
    //cria os objetos e variáveis***********************************************************
    JLabel lblLogin, lblUser, lblSenha;
    JTextField txtUser;
    JPasswordField pwdSenha;
    JRadioButton radio[];
    ButtonGroup tipoUsuario = new ButtonGroup();
    JButton btnRegistrar, btnEntrar;
    
    public WindowLogin() {
        //configura o título da janela******************************************************
        super(":: LOGIN ::");
        
        //atribui valores aos objetos*******************************************************
        lblLogin = new JLabel("LOGIN");
        lblUser = new JLabel("usuário");
        lblSenha = new JLabel("senha");
        txtUser = new JTextField(17);
        pwdSenha = new JPasswordField(17);
        radio = new JRadioButton[2];
        radio[0] = new JRadioButton("Funcionário");
        radio[1] = new JRadioButton("Cliente");
        btnRegistrar = new JButton("REGISTRAR");
        btnEntrar = new JButton("ENTRAR");
        
        //chama métodos para os objetos****************************************************
        
        /*********método para o botão registrar**************/
        btnRegistrar.addActionListener(
            new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    WindowRegister registrar = new WindowRegister();
                    registrar.setVisible(true);
                }
            }
        );
        
        /*********método para o botão entrar****************/
        btnEntrar.addActionListener(
            new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    
                }
            }
        );
                
        
        //cria painel norte*****************************************************************
        JPanel painelNorte = new JPanel();
        
        painelNorte.add(lblUser);
        painelNorte.add(txtUser);
        
        //cria o painel central*************************************************************
        JPanel painelCentral = new JPanel();
        
        painelCentral.add(lblSenha);
        painelCentral.add(pwdSenha);
        
        //cria painel sul*******************************************************************
        JPanel painelSul = new JPanel();
        
        painelSul.add(btnRegistrar);
        painelSul.add(btnEntrar);
        
        //cria painel principal**************************************************************
        JPanel painelPrincipal = new JPanel(new GridLayout(3, 1));
        
        painelPrincipal.add(painelNorte);
        painelPrincipal.add(painelCentral);
        painelPrincipal.add(painelSul);
        
        //cria o painel principal de toda janela***********************************************
        Container container = getContentPane();
        
        container.add(painelPrincipal);
        
        //chama métodos para a janela******************************************************
        pack();
        setSize(200, 170);
        setResizable(false);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

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

class WindowRegister extends JFrame {
    JLabel lblSenhaMaster;
    JTextField pwdSenhaMaster;
    JButton btnAvancar;
    
    public WindowRegister() {
        //configura o título da janela
        super("|| Administrator :: Cadastro :: Senha Master ||");
        
        //atribui valores aos objetos e variáveis
        lblSenhaMaster = new JLabel("Insira a senha");
        pwdSenhaMaster = new JTextField(15);
        btnAvancar = new JButton("Avançar >");
        final String SENHAMASTER = "020716";
        
        //métodos para os campos************************************************************
        /***********metodo para botão avançar****************/
        btnAvancar.addActionListener(
            new ActionListener() {
                public void actionPerformed (ActionEvent e) {
                    String txtSenha = pwdSenhaMaster.getText();
                    if(txtSenha != SENHAMASTER) {
                        pwdSenhaMaster.setBackground(Color.RED);
                    }
                    else {
                        setVisible(false);
                    }
                }
            }
        );
        
        //cria painel principal****************************************************************
        JPanel painel = new JPanel();
        
        painel.add(lblSenhaMaster);
        painel.add(pwdSenhaMaster);
        painel.add(btnAvancar);
        
        //cria o painel
        
        //cria o container*******************************************************************
        Container container = getContentPane();
        container.add(painel);
        
        pack();
        setSize(200, 170);
    }
}

class Programa {
    public static void main(String[] args) {
        WindowLogin login = new WindowLogin();
        WindowRegister registrar = new WindowRegister();
    }
}