package View;

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.JTextField;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JPasswordField;

public class AdminUI2 extends JFrame {

    private JLabel lblUserID;
    private JLabel lblName;
    private JLabel lblSurname;
    private JLabel lblPassword;
    private JLabel lblCodiceFiscale;

    private JTextField textFieldUserID;
    private JTextField textFieldName;
    private JTextField textFieldSurname;
    private JTextField textFieldCodiceFiscale;
    private JPasswordField textFieldPassword;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    AdminUI frame = new AdminUI();
                    frame.setTitle("AdminUI");
                    frame.setVisible(true);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public AdminUI2() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 574, 512);
        setTitle("User Management");

        JTabbedPane tabbedPane = new JTabbedPane();

        JPanel panel1 = new JPanel();
        lblUserID = new JLabel("UserID:");
        lblUserID.setBounds(10, 47, 37, 14);
        lblName = new JLabel("Name:");
        lblName.setBounds(10, 87, 46, 14);
        lblSurname = new JLabel("Surname:");
        lblSurname.setBounds(10, 130, 46, 14);
        lblPassword = new JLabel("Password:");
        lblPassword.setBounds(10, 176, 63, 14);
        lblCodiceFiscale = new JLabel("Codice Fiscale:");
        lblCodiceFiscale.setBounds(10, 221, 78, 14);

        textFieldUserID = new JTextField();
        textFieldUserID.setBounds(98, 44, 46, 20);
        textFieldUserID.setColumns(5);
        textFieldName = new JTextField();
        textFieldName.setBounds(98, 84, 86, 20);
        textFieldName.setColumns(10);
        textFieldSurname = new JTextField();
        textFieldSurname.setBounds(98, 127, 86, 20);
        textFieldSurname.setColumns(10);
        textFieldCodiceFiscale = new JTextField();
        textFieldCodiceFiscale.setBounds(98, 218, 176, 20);
        textFieldCodiceFiscale.setColumns(10);
        textFieldPassword = new JPasswordField();
        textFieldPassword.setBounds(98, 173, 86, 20);
        JButton btnRegisterUser = new JButton("Register");
        btnRegisterUser.setBounds(95, 292, 89, 23);
        panel1.setLayout(null);
        panel1.add(lblName);
        panel1.add(lblSurname);
        panel1.add(lblPassword);
        panel1.add(lblCodiceFiscale);
        panel1.add(lblUserID);
        panel1.add(textFieldUserID);
        panel1.add(textFieldName);
        panel1.add(textFieldSurname);
        panel1.add(textFieldCodiceFiscale);
        panel1.add(textFieldPassword);
        panel1.add(btnRegisterUser);

        tabbedPane.addTab("Register User", panel1);

        JPanel panel2 = new JPanel();
        tabbedPane.addTab("Register Client", panel2);

        JPanel panel3 = new JPanel();
        tabbedPane.addTab("Modify User Data", panel3);

        JPanel panel4 = new JPanel();
        tabbedPane.addTab("Users and Clients", panel4);

        JPanel panel5 = new JPanel();
        tabbedPane.addTab("Add User Parameters", panel5);

        JPanel panel6 = new JPanel();
        tabbedPane.addTab("Policies", panel6);

        getContentPane().add(tabbedPane);

    }
}

public class PanelRegistroUsuario extends JPanel() {
     ... atributos
     public PanelRegistroUsuario() {
         ... código inicialización
     }

     ... getters y setters para acceder a los valores de los componentes, si es necesario.
 }

JTabbedPane tabbedPane = new JTabbedPane();
    tabbedPane.addTab("Register User", new PanelRegistroUsuario());