如何在一个月内获得序数平日

Question

嗨我想在java中创建一个程序,其中days,weekNo是参数..类似于月的第一个星期五或月的第二个星期一..它返回日期

Answer 1

这里有一个,做的是,用实用的方法DateUtils从阿帕奇百科全书/郎咸平:

/**
 * 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:

2010年11月18日00:00:00 CET 2010年
12月8 日星期三00:00:00 CET 2010

这里是相同代码的JodaTime版本(之前我从未使用过JodaTime,所以可能有一种更简单的方法):

/**
 * 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