Loop in hour interval

I need to walk through a time slot to set up a schedule grid. Example: 8:00 AM to 10:00 AM, adding 30 minutes. Forming a grid like this: 8 o'clock 08:30 09:00 09:30 10:00

I'm trying like this:

    GregorianCalendar gc = new GregorianCalendar();
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");

    Date hInicial = null, hFinal = null;

    try {
        hInicial = sdf.parse("08:00");
        hFinal = sdf.parse("10:00");
    } catch (ParseException e) {
        e.printStackTrace();
    }

    GregorianCalendar inicio = new GregorianCalendar();
    inicio.setTime(hInicial);
    GregorianCalendar fim = new GregorianCalendar();
    fim.setTime(hFinal);

    gc.setTime(hInicial);
    while(!inicio.after(fim)) {

        gc.add(Calendar.MINUTE, 30);

    }

The system is in infinite loop.

Thank you in advance.