public List<User> selectUsers() {
        List<User> user = new LinkedList<User>();
        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");
                user.add(new User(id_user, login, password));
            }
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
        return user;
    }