Ошибка написание интерфейса для mail client - Java

Формулировка задачи:

Добрый день. Недавно начал осваивать написание мэйл клиентов на java. У меня есть код, но и имеется маленькая ошибка с геттером. На вид очень простая, но мне не по зубам. Помогите пожалуйста. Вот сама ошибка:

public String getType() {
        return (String) typeComboBox.getSelectedItem();

А Вот весь код:

package javamailproject;
 
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JOptionPane;
 
public class ConnectDialog extends javax.swing.JDialog {
 
    public ConnectDialog(java.awt.Frame parent) {
        super(parent, true);
        setTitle("Connection...");
 
        addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                actionCancel();
            }
        });
        setLocationRelativeTo(parent);
        initComponents();
    }
 
    private void actionConnect() {
        if (serverTextField.getText().trim().length() < 1
                || usernameTextField.getText().trim().length() < 1
                || passwordField.getPassword().length < 1
                || smtpServerTextField.getText().trim().length() < 1) {
            JOptionPane.showMessageDialog(this, "Error!", "Fill all gaps!", JOptionPane.ERROR_MESSAGE);
            return;
        }
 
        dispose();
    }
 
    private void actionCancel() {
        System.exit(0);
    }
 
    public String getType() {
        return (String) typeComboBox.getSelectedItem();
    }
 
    public String getServer() {
        return serverTextField.getText();
    }
 
    public String getUsername() {
        return usernameTextField.getText();
    }
 
    public String getPassword() {
        return new String(passwordField.getPassword());
    }
 
    public String getSmtpServer() {
        return smtpServerTextField.getText();
    }
 
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
 
        connectPanel = new javax.swing.JPanel();
        typeLabel = new javax.swing.JLabel();
        typeComboBox = new javax.swing.JComboBox();
        serverLabel = new javax.swing.JLabel();
        serverTextField = new javax.swing.JTextField();
        usernameLabel = new javax.swing.JLabel();
        usernameTextField = new javax.swing.JTextField();
        passwordLabel = new javax.swing.JLabel();
        smtpServerLabel = new javax.swing.JLabel();
        smtpServerTextField = new javax.swing.JTextField();
        passwordField = new javax.swing.JPasswordField();
        connectButton = new javax.swing.JButton();
        cancelButton = new javax.swing.JButton();
 
        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
 
        connectPanel.setBorder(javax.swing.BorderFactory.createTitledBorder(javax.swing.BorderFactory.createEtchedBorder(), "Установка соединения"));
 
        typeLabel.setText("Тип протокола:");
 
        typeComboBox.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "pop3" }));
 
        serverLabel.setText("Сервер:");
 
        usernameLabel.setText("Имя пользователя:");
 
        passwordLabel.setText("Пароль:");
 
        smtpServerLabel.setText("SMTP сервер:");
 
        passwordField.setText("jPasswordField1");
 
        javax.swing.GroupLayout connectPanelLayout = new javax.swing.GroupLayout(connectPanel);
        connectPanel.setLayout(connectPanelLayout);
        connectPanelLayout.setHorizontalGroup(
            connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(connectPanelLayout.createSequentialGroup()
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(connectPanelLayout.createSequentialGroup()
                        .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(passwordLabel)
                            .addComponent(usernameLabel)
                            .addComponent(smtpServerLabel))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED))
                    .addComponent(serverLabel)
                    .addGroup(connectPanelLayout.createSequentialGroup()
                        .addComponent(typeLabel)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)))
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(typeComboBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(serverTextField, javax.swing.GroupLayout.DEFAULT_SIZE, 150, Short.MAX_VALUE)
                    .addComponent(smtpServerTextField, javax.swing.GroupLayout.DEFAULT_SIZE, 150, Short.MAX_VALUE)
                    .addComponent(usernameTextField, javax.swing.GroupLayout.DEFAULT_SIZE, 150, Short.MAX_VALUE)
                    .addComponent(passwordField, javax.swing.GroupLayout.DEFAULT_SIZE, 150, Short.MAX_VALUE))
                .addContainerGap())
        );
        connectPanelLayout.setVerticalGroup(
            connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(connectPanelLayout.createSequentialGroup()
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(typeComboBox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(typeLabel))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(serverTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(serverLabel))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(usernameLabel)
                    .addComponent(usernameTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(passwordLabel)
                    .addComponent(passwordField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(connectPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(smtpServerTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(smtpServerLabel)))
        );
 
        connectButton.setText("OK");
        connectButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                connectButtonMouseClicked(evt);
            }
        });
 
        cancelButton.setText("Отмена");
        cancelButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                cancelButtonMouseClicked(evt);
            }
        });
 
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(connectPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addGroup(layout.createSequentialGroup()
                .addGap(38, 38, 38)
                .addComponent(connectButton, javax.swing.GroupLayout.PREFERRED_SIZE, 83, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(cancelButton, javax.swing.GroupLayout.PREFERRED_SIZE, 93, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(53, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(connectPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(connectButton)
                    .addComponent(cancelButton))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
 
        pack();
    }// </editor-fold>                        
 
    private void connectButtonMouseClicked(java.awt.event.MouseEvent evt) {                                           
        actionConnect();
    }                                          
 
    private void cancelButtonMouseClicked(java.awt.event.MouseEvent evt) {                                          
        actionCancel();
    }                                         
 
    // Variables declaration - do not modify                     
    private javax.swing.JButton cancelButton;
    private javax.swing.JButton connectButton;
    private javax.swing.JPanel connectPanel;
    private javax.swing.JPasswordField passwordField;
    private javax.swing.JLabel passwordLabel;
    private javax.swing.JLabel serverLabel;
    private javax.swing.JTextField serverTextField;
    private javax.swing.JLabel smtpServerLabel;
    private javax.swing.JTextField smtpServerTextField;
    private javax.swing.JComboBox typeComboBox;
    private javax.swing.JLabel typeLabel;
    private javax.swing.JLabel usernameLabel;
    private javax.swing.JTextField usernameTextField;
    // End of variables declaration                   
 
}

Заранее огромное спасибо!

Решение задачи: «Ошибка написание интерфейса для mail client»

textual
                            Листинг программы 
                        
                            return typeComboBox.getSelectedItem().toString()