public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Connection con;
        Statement st;
        ResultSet rs;
        String test;
        String url = "jdbc:mysql://localhost/userzy"; //w miejscu kropek należy podać nazwę bazy
        System.out.println("Login:");
        String user = sc.nextLine();
        System.out.println("Hasło:");
        String pass = sc.nextLine();
        try {
            con = DriverManager.getConnection(url, user, pass);
        do{
        System.out.println("wybierz opcję a,b,c lub d: ");
        switch (test=sc.nextLine()) {
            case "a": {
                try {
                    con = DriverManager.getConnection(url, user, pass);
                    st = con.createStatement();
                    System.out.println("Wyświetlanie danych: ");
                    rs = st.executeQuery("SELECT * FROM dane_osobowe"); //zapytanie SQL
                    while (rs.next()) {
                        System.out.println(rs.getString(1) + " " + rs.getString(2) + " " + rs.getString(3));
                    }
                } catch (SQLException ex) {
                    System.out.println("błąd SQL");
                }
                break;
            }
            case "b": {
                try {
                    con = DriverManager.getConnection(url, user, pass);
                    st = con.createStatement();
                    System.out.println("Podaj dane do dodania: ");
                    String input = sc.nextLine();
                    String[] array = input.split(" ");
                    String sql="INSERT INTO dane_osobowe (id, Imie, Nazwisko) VALUES (?, ?, ?)"; //zapytanie SQL
                    PreparedStatement pst = con.prepareStatement(sql);
                    pst.setString(1, array[0]);
                    pst.setString(2, array[1]);
                    pst.setString(3, array[2]);
                    pst.execute();
                } catch (SQLException ex) {
                    System.out.println("błąd SQL");
                }
                break;
            }
            case "c": {
                try {
                    con = DriverManager.getConnection(url, user, pass);
                    st = con.createStatement();
                    rs = st.executeQuery("SELECT * FROM dane_osobowe"); //zapytanie SQL
                    while (rs.next()) {
                        System.out.println(rs.getString(1) + " " + rs.getString(2) + " " + rs.getString(3));
                    }
                    System.out.println("Podaj id danej, które chcesz usunąć: ");
                    String input = sc.nextLine();                    String[] array = input.split(" ");
                    String sql="DELETE FROM dane_osobowe WHERE id= ?"; //zapytanie SQL
                    PreparedStatement pst = con.prepareStatement(sql);
                    pst.setString(1, input);
                    pst.execute();
                } catch (SQLException ex) {
                    System.out.println("błąd SQL");
                }
                break;
            }
            case "d": {
                try {
                    con = DriverManager.getConnection(url, user, pass);
                    st = con.createStatement();
                    System.out.println("Według czego posortować tabele (id, Imie, Nazwisko)?: ");
                    String input = sc.nextLine();
                    rs = st.executeQuery("SELECT * FROM dane_osobowe ORDER BY " + input);
                    while (rs.next()) {
                        System.out.println(rs.getString(1) + " " + rs.getString(2) + " " + rs.getString(3));
                    }
                } catch (SQLException ex) {
                    System.out.println("błąd SQL");
                }
                break;
            }

        }}while(!test.equals("exit"));
        }catch (SQLException ex) {
                    System.out.println("Bład logowania");
                }
    }

}