java - 如何获得一个月中的序数工作日

Question

嗨，我想在 java 中制作一个程序，其中 days,weekNo 是参数..就像每月的第一个星期五或每月的第二个星期一..它返回日期

Answer 1

这是一个实用方法，使用 DateUtils来自 Apache Commons / Lang :

/**
 * Get the n-th x-day of the month in which the specified date lies.  
 * @param input the specified date
 * @param weeks 1-based offset (e.g. 1 means 1st week)
 * @param targetWeekDay (the weekday we're looking for, e.g. Calendar.MONDAY
 * @return the target date
 */
public static Date getNthXdayInMonth(final Date input,
    final int weeks,
    final int targetWeekDay){

    // strip all date fields below month
    final Date startOfMonth = DateUtils.truncate(input, Calendar.MONTH);
    final Calendar cal = Calendar.getInstance();
    cal.setTime(startOfMonth);
    final int weekDay = cal.get(Calendar.DAY_OF_WEEK);
    final int modifier = (weeks - 1) * 7 + (targetWeekDay - weekDay);
    return modifier > 0
        ? DateUtils.addDays(startOfMonth, modifier)
        : startOfMonth;
}

测试代码:

// Get this month's third thursday
System.out.println(getNthXdayInMonth(new Date(), 3, Calendar.THURSDAY));

// Get next month's second wednesday:
System.out.println(getNthXdayInMonth(DateUtils.addMonths(new Date(), 1),
    2,
    Calendar.WEDNESDAY)
);

输出:

Thu Nov 18 00:00:00 CET 2010
Wed Dec 08 00:00:00 CET 2010

---

这是一个 JodaTime相同代码的版本(我以前从未使用过 JodaTime，所以可能有更简单的方法来实现):

/**
 * Get the n-th x-day of the month in which the specified date lies.
 * 
 * @param input
 *            the specified date
 * @param weeks
 *            1-based offset (e.g. 1 means 1st week)
 * @param targetWeekDay
 *            (the weekday we're looking for, e.g. DateTimeConstants.MONDAY
 * @return the target date
 */
public static DateTime getNthXdayInMonthUsingJodaTime(final DateTime input,
    final int weeks,
    final int targetWeekDay){

    final DateTime startOfMonth =
        input.withDayOfMonth(1).withMillisOfDay(0);
    final int weekDay = startOfMonth.getDayOfWeek();
    final int modifier = (weeks - 1) * 7 + (targetWeekDay - weekDay);
    return modifier > 0 ? startOfMonth.plusDays(modifier) : startOfMonth;
}

测试代码:

// Get this month's third thursday
System.out.println(getNthXdayInMonthUsingJodaTime(new DateTime(),
    3,
    DateTimeConstants.THURSDAY));

// Get next month's second wednesday:
System.out.println(getNthXdayInMonthUsingJodaTime(new DateTime().plusMonths(1),
    2,
    DateTimeConstants.WEDNESDAY));

输出:

2010-11-18T00:00:00.000+01:00
2010-12-08T00:00:00.000+01:00