Calendar.DAY_OF_WEEK_IN_MONTH等效于java8中的ZonedDateTime

Question

I am trying to check Thanksgiving (4th Thursday of November).
I have ZonedDateTime as 2019-11-23T08:43:14.699-07:00[America/Los_Angeles]

How do I check whether it is4th Thursday or not using java 8 ZonedDateTime api

In calendar we have Calendar.DAY_OF_WEEK_IN_MONTH to calculate the week number of in a month. Is there any such thing in ZonedDateTime ?

I have this using calendar.

// check Thanksgiving (4th Thursday of November)
    if (cal.get(Calendar.MONTH) == Calendar.NOVEMBER
        && cal.get(Calendar.DAY_OF_WEEK_IN_MONTH) == 4
        && cal.get(Calendar.DAY_OF_WEEK) == Calendar.THURSDAY) {
        return false;
    }

How can I achieve this using ZonedDateTime ?

Answer 1

What you need is the aligned week of month. The first aligned week of the month is from the 1 through the 7 of the month, so contains the first Thursday of the month no matter on which day of the week the month begins. The second aligned week is 8 through 14 of the month, etc.

    ZonedDateTime zdt = ZonedDateTime.parse("2019-11-23T08:43:14.699-07:00[America/Los_Angeles]");
    if (zdt.getMonth().equals(Month.NOVEMBER)
            && zdt.get(ChronoField.ALIGNED_WEEK_OF_MONTH) == 4
            && zdt.getDayOfWeek().equals(DayOfWeek.THURSDAY)) {
        System.out.println("" + zdt + " is on Thanksgiving");
    }

Since Thanksgiving is on November 28 this year, the above snippet testing November 23 doesn't print anything. Try with the right day instead:

    ZonedDateTime zdt = ZonedDateTime.parse("2019-11-28T17:34:56.789-07:00[America/Los_Angeles]");

2019-11-28T16:34:56.789-08:00[America/Los_Angeles] is on Thanksgiving