Easiest way to set past/future date in Java 8

Question

I have a solution for setting future/past date Java 8, but I would like to know if there is a cleaner way. I have a method in which one of the argument is of type ZonedDateTime.

I am extracting the time, converting to milliseconds and subtracting that from present now.

void setFuturePastDate(ZonedDateTime dateTime) {
    long diffInSeconds = ZonedDateTime.now().toEpochSecond() 
        - dateTime.toEpochSecond();
    Duration durationInSeconds = Duration.ofSeconds(diffInSeconds);
    Instant instantInSeconds = now.minusSeconds(durationInSeconds); 
    Clock clock = Clock.fixed(instantInSeconds, ZoneId.systemDefault());
    System.out.println(ZonedDateTime.now(clock)); // - I have a past date

In Joda it was simple:

setCurrentMillisSystem(long)

and wherever we access new DateTime() it will give the date set.

Is there a cleaner way in Java 8 ?

sorry for that, will keep it in mind. accepted the answer by Ole — Parameswar, Jul 19 '18 at 12:34

score 1 · Accepted Answer · answered Jul 19 '18 at 12:23

1

void setFuturePastDate(ZonedDateTime dateTime) {
    Clock clock = Clock.fixed(dateTime.toInstant(), ZoneId.systemDefault());
    System.out.println(ZonedDateTime.now(clock)); // - I have a past date 
}

This method prints the same ZonedDateTime as I passed in (provided it has the default zone).

answered Jul 19 '18 at 12:23

Ole V.V.

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Yes,Best way..... – NullPointer Jul 19 '18 at 14:32

score 0 · Answer 2 · answered Jul 19 '18 at 12:32

If I understood you correctly, this is what you want:

void setFuturePastDate(LocalDateTime dateTime){
    final LocalDateTime now = LocalDateTime.now();
    final Duration duration = Duration.between(now, dateTime);
    final LocalDateTime mirrored;
    if(duration.isNegative()){
        mirrored = now.minus(duration);
    } else {
        mirrored = now.plus(duration);
    }

    System.out.println(mirrored);
}

This mirrors the dateTime around the now(). E.g: 5 days in the past becomes 5 days in the future.

Easiest way to set past/future date in Java 8

2 Answers2