On Dec 21, 2008, at 6:34 PM, Stephen Colebourne wrote:
> Joda-Time doesn't have anything to help with this particular
> calculation
> (JSR-310 does).
I'm new to Joda-Time. Perhaps some of my assumptions were wrong. I
thought JSR-310 was all based on Joda-Time and assumed that anything
new in JSR-310 would be tested by adding it to Joda-Time. When you say
JSR-310 has it, do you mean that it's in the spec or that there is
different library I could download now that has it?
Here's the implementation I came up with. If it looks useful, feel
free to add it to Joda-Time under whatever name you think is best.
/**
* Gets the nth given weekday of a given month.
* For example, to find the 4th Thursday of the month of November
in 2008,
* getNthWeekday(2008, 11, DateTimeConstants.THURSDAY, 4)
* @param year the year
* @param month the month
* @param weekday the day of the week (such as Thursday)
* @param n the number of that day within the month (such as the
4th)
* @return the LocalDate
*/
private static LocalDate getNthWeekday(
int year, int month, int weekday, int n) {
// Get the 1st day of the month.
LocalDate ld = new LocalDate(year, month, 1);
// Determine the number of days to advance to get to
// the first requested weekday of the month.
int firstWeekday = ld.getDayOfWeek();
int diff = (7 - firstWeekday + weekday) % 7;
return ld.plusDays(diff).plusWeeks(n - 1);
}
> The withDayfWeek() method adjusts the day within the current Monday to
> Sunday week.
>
> Stephen
>
>
> Kevin Bourrillion wrote:
>> I was wondering the same thing just yesterday.
>>
>>
>> On Fri, Dec 19, 2008 at 7:02 AM, Mark Volkmann <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> LocalDate ld = new LocalDate(year, 11, 1);
>> if (ld.getDayOfWeek() != DateTimeConstants.THURSDAY) {
>>
>>
>> At this point, 'd.plusDays(THURSDAY - d.getDayOfWeek() + 7) % 7)'
>> should
>> get you straight to the first Thursday, right? I don't know what's
>> the
>> best way, though. I also couldn't find an explanation of what
>> .withDayOfWeek() does -- does it always move backward?
>>
>> K
>>
>> // Move back to the previous Thursday.
>> ld = ld.withDayOfWeek(DateTimeConstants.THURSDAY);
>>
>> if (ld.monthOfYear().get() !=
>> DateTimeConstants.NOVEMBER) {
>> ld = ld.plusWeeks(1); // move forward into
>> November
>> }
>> }
>>
>> return ld.plusWeeks(3); // to get to 4th Thursday
>> }
>> }
>>
>> // Now call that method like this.
>> LocalDate thanksgiving = getThanksgiving(year);
>> if (thanksgiving.isBefore(today)) {
>> thanksgiving = getThanksgiving(year + 1);
>> }
---
Mark Volkmann
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