Java 返回一个日期加多少分钟后的日期

public static String addDateMinut(String day, int x) {
		SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");// 24小时制
		Date date = null;
		try {
			date = format.parse(day);
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		if (date == null)
			return "";
		System.out.println("front:" + format.format(date));
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		cal.add(Calendar.MINUTE, x);// 24小时制
		date = cal.getTime();
		System.out.println("after:" + format.format(date));
		cal = null;
		return format.format(date);

	}