public static String secondToTime(int seconds) {
		if (seconds < 0) {
			throw new IllegalArgumentException("Seconds must be a positive number!");
		}

		int hour = seconds / 3600;
		int other = seconds % 3600;
		int minute = other / 60;
		int second = other % 60;
		final StringBuilder sb = new StringBuilder();
		if (hour < 10) {
			sb.append("0");
		}
		sb.append(hour);
		sb.append(":");
		if (minute < 10) {
			sb.append("0");
		}
		sb.append(minute);
		sb.append(":");
		if (second < 10) {
			sb.append("0");
		}
		sb.append(second);
		return sb.toString();
	}
@Test
	public void secondToTimeTest() {
		String time = DateUtil.secondToTime(3600);
		assertEquals("01:00:00", time);
		time = DateUtil.secondToTime(3800);
		assertEquals("01:03:20", time);
		time = DateUtil.secondToTime(0);
		assertEquals("00:00:00", time);
		time = DateUtil.secondToTime(30);
		assertEquals("00:00:30", time);
	}