Java 获取当前天是一年中的第几天

Java 获取当前天是一年中的第几天

@Test
void dayofweed() throws Exception {
    System.out.println("2023-01-01 第 " + getWeekYearISO("2023-01-01"));
    System.out.println("2023-08-01 第 " + getWeekYearISO("2023-08-01"));
}


public static int getWeekYearISO(String today) throws ParseException {
    SimpleDateFormat df_yyyyMMdd = new SimpleDateFormat("yyyy-MM-dd");
    Date date = df_yyyyMMdd.parse(today);
    Calendar calendar = Calendar.getInstance();

    calendar.setFirstDayOfWeek(Calendar.MONDAY); // 每周一算开始
    calendar.setMinimalDaysInFirstWeek(4);  // 一周最少要有 4 天，默认：1
    calendar.setTime(date);
    return  calendar.get(Calendar.WEEK_OF_YEAR);

}

2023-01-01 第 52
2023-08-01 第 31