android - How to display time adding 30mins from current time

I just want it to be displayed from current time adding 30mins till day ends
Ex-Today time is 09:46AM
It should display like 10:00AM,10:30AM,11:00AM....11:30PM for that particular date.

But here in my code its displaying from 00:00...23:30 for whole day.
Here is my code:

SimpleDateFormat df = new SimpleDateFormat("HH:mm");
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        int startDate = cal.get(Calendar.DATE);
        while (cal.get(Calendar.DATE) == startDate) {

            Log.d("time","currenttime"+cal.getTime());
            cal.add(Calendar.MINUTE, 30);
        }