Is there a good way to get the date of the coming Wednesday?

Question

Is there a good way to get the date of the coming Wednesday? That is, if today is Tuesday, I want to get the date of Wednesday in this week; if today is Wednesday, I want to get the date of next Wednesday; if today is Thursday, I want to get the date of Wednesday in the following week.

Thanks.

Answer 1

tl;dr

LocalDate                        // Represent a date-only value, without time-of-day and without time zone.
.now()                           // Capture the current date as seen in the wall-clock time used by the people of a specific region (a time zone). The JVM’s current default time zone is used here. Better to specify explicitly your desired/expected time zone by passing a `ZoneId` argument. Returns a `LocalDate` object.
.with(                           // Generate a new `LocalDate` object based on values of the original but with some adjustment. 
    TemporalAdjusters            // A class that provides some handy pre-defined implementations of `TemporalAdjuster` (note the singular) interface.
    .next(                       // An implementation of `TemporalAdjuster` that jumps to another date on the specified day-of-week.
        DayOfWeek.WEDNESDAY      // Pass one of the seven predefined enum objects, Monday-Sunday.
    )                            // Returns an object implementing `TemporalAdjuster` interface.
)                                // Returns a `LocalDate` object.

Details

Using Java8 Date time API you can easily find the coming Wednesday.

LocalDate nextWed = LocalDate.now().with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));

next(DayOfWeek dayOfWeek) - Returns the next day-of-week adjuster, which adjusts the date to the first occurrence of the specified day-of-week after the date being adjusted.

Suppose If you want to get previous Wednesday then,

LocalDate prevWed = LocalDate.now().with(TemporalAdjusters.previous(DayOfWeek.WEDNESDAY));

previous(DayOfWeek dayOfWeek) - Returns the previous day-of-week adjuster, which adjusts the date to the first occurrence of the specified day-of-week before the date being adjusted.

Suppose If you want to get next or current Wednesday then

LocalDate nextOrSameWed = LocalDate.now().with(TemporalAdjusters.nextOrSame(DayOfWeek.WEDNESDAY));

nextOrSame(DayOfWeek dayOfWeek) - Returns the next-or-same day-of-week adjuster, which adjusts the date to the first occurrence of the specified day-of-week after the date being adjusted unless it is already on that day in which case the same object is returned.

Edit: You can also pass ZoneId to get the current date from the system clock in the specified time-zone.

ZoneId zoneId = ZoneId.of("UTC");
LocalDate nextWed = LocalDate.now(zoneId).with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));

For more information refer TemporalAdjusters

Answer 2

The basic algorithm is the following:

• Get the current date
• Get its day of week
• Find its difference with Wednesday
• If the difference is not positive, add 7 (i.e. insist on next coming/future date)
• Add the difference

Here's a snippet to show how to do this with java.util.Calendar:

import java.util.Calendar;

public class NextWednesday {
    public static Calendar nextDayOfWeek(int dow) {
        Calendar date = Calendar.getInstance();
        int diff = dow - date.get(Calendar.DAY_OF_WEEK);
        if (diff <= 0) {
            diff += 7;
        }
        date.add(Calendar.DAY_OF_MONTH, diff);
        return date;
    }
    public static void main(String[] args) {
        System.out.printf(
            "%ta, %<tb %<te, %<tY",
            nextDayOfWeek(Calendar.WEDNESDAY)
        );
    }
}

Relative to my here and now, the output of the above snippet is "Wed, Aug 18, 2010".

API links

• java.util.Calendar
• java.util.Formatter - for the formatting string syntax