public DefaultTableModel getData()
    {
        DefaultTableModel table=new DefaultTableModel();
        table.addColumn("ID");
        table.addColumn("Login");
        table.addColumn("Haslo");

        try {
            ResultSet result = stat.executeQuery("SELECT * FROM Users");
            int id_user;
            String login,password;
            while(result.next()) {
                id_user=result.getInt("id_user");
                login = result.getString("login");
                password = result.getString("password");
                table.addRow(new String[]{"1", login, password});
            }
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
        return table;
    }
package gui;

import Data_base_shop.Users;

import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;


public class manage_users extends JFrame
{
    private JPanel panel;
    private JButton wrócDoPaneluButton;
    private JButton usuńUżytkownikaButton;
    private JTable table1;
    public TableModel tableModel;

    public manage_users()
    {
        super("Zarządzanie użytkownikami");
        setContentPane(panel);
        pack();
        setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);

        setVisible(true);
        setLocation(600,150);


        addWindowListener(new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent e) {
                if(JOptionPane.showConfirmDialog(null, "Czy chcesz wrócić?") == JOptionPane.OK_OPTION){
                    new admin_screen();
                    dispose();
                }
            }
        });

        wrócDoPaneluButton.addActionListener(new ActionListener()
        {

            @Override
            public void actionPerformed(ActionEvent e)
            {
                new admin_screen();
                dispose();
            }
        });

    }



    public static void main(String[] args) {
        new manage_users();
    }

    private void table_Users()
    {

   }

}