GregorianCalendar gcalendar = new GregorianCalendar();

int ore = 2;
int minuti = 5;
int secondi = 0;

while (ore >= 0) {
    gcalendar.set(Calendar.HOUR, ore);
    while (minuti >= 0) {
        gcalendar.set(Calendar.MINUTE, minuti);
        while (secondi >= 0) {
            gcalendar.set(Calendar.SECOND, secondi);
            System.out.println(gcalendar.get(Calendar.MINUTE)+":"+gcalendar.get(Calendar.SECOND));
            try {
                Thread.sleep(1000L);
            } catch(InterruptedException _ex) {}
            secondi--;
        }
        minuti--;
        secondi = 59;
    }
    ore--;
    minuti = 59;
}