判断输入日期是该年的第一天

public static void main(String[] args) {
		try {
			dayOfYear("2002-01-02");
		} catch (ParseException e) {
			e.printStackTrace();
		}
	}

	private static void dayOfYear(String dateStart) throws ParseException{
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-HH-dd");
        Date date = sdf.parse(dateStart);
        Calendar calendar = Calendar.getInstance(); 
        calendar.setTime(date); 
        int y = calendar.get(Calendar.DAY_OF_YEAR);
        System.out.println("Day of year:" + y + " of " + date);

	}