Get seconds between next day with time-CodePudding

I am trying to get the Duration until the next time, depending on a Day of Week in Java.

I want to be able to schedule a Java task for the next day in a list, at a specific time, so for example, with a list of Monday and Thursday, and it is Sunday, I want to get the seconds until the Monday at a specific time based on hours and minutes passed into the method.

This means that if the current day is Sunday at 10:00AM, and I pass in the time 09:00, I want to go to the next day in the list.

Examples:

daysToFire = ['Monday', 'Wednesday', 'Friday', 'Sunday']

hours = 10

minutes = 10

On Monday 11:00, I want to get the Duration until Wednesday 10:10
On Monday 09:00 I want to get the Duration until Monday 10:10
On Sunday 20:00 I want to get the Duration until Monday 10:10
On Wednesday 13:00 I want to get the Duration until Friday 10:10

My current method always goes out at the last return.

private Duration getDurationUntilNext(int hours, int minutes) {
final Instant instant = Instant.now(Clock.system(timeZone));

final DayOfWeek currentDay = instant.atZone(timeZone).getDayOfWeek();

final ZonedDateTime currentZonedDateTime = instant.atZone(timeZone);

for(DayOfWeek dayOfWeek : daysToFire) {
    if(currentDay == dayOfWeek) {
        final ZonedDateTime nextTime = currentZonedDateTime
                .with(TemporalAdjusters.nextOrSame(currentDay))
                .withHour(hours)
                .withMinute(minutes)
                .withSecond(0);

        if(nextTime.isAfter(currentZonedDateTime))
            return Duration.between(currentZonedDateTime, nextTime);
    }
}

return Duration.ZERO;

}

If anyone can help, that would be very much appreciated. Thank you all for the help already!

CodePudding user response：

By the way, you could shorten Instant.now(Clock.system(timeZone)) to Instant.now().

Define the time zone by which you want to recognize date and time.

ZoneId z = ZoneId.of( "Africa/Tunis" ) ;

Capture the current moment as seen in that zone.

ZonedDateTime now = ZonedDateTime.now( z ) ;

Define your list of day-of-week.

List< DayOfWeek > dows = List.of( DayOfWeek.MONDAY , DayOfWeek.THURSDAY ) ;

Specify your target time of day.

LocalTime targetTime = LocalTime.of( 10 , 0 ) ;

For each day of week, adjust the current moment to that day of week at that time.

TemporalAdjuster ta = TemporalAdjusters.nextOrSame( dow ) ;
ZonedDateTime zdt = now.with( ta ).with( targetTime ) ;

Be aware that your target time may not exist on that date in that zone. A further adjustment will be made automatically as needed.

Calculate duration.

Duration d = Duration.between ( now , zdt ) ;

Test to see if negative. A negative duration means we are going backward in time, means zdt came before now. When encountering a negative duration, we need to use a temporal adjuster of next rather than nextOrSame.

if( d.isNegative() ) {  // If zdt is in the past …
    zdt = zdt.with( TemporalAdjusters.next( dow ) ).with( targetTime ) ;
}

Notice that java.time uses immutable objects. So zdt.with generates a new fresh instance of ZonedDateTime rather than altering (“mutating”) the original.

Recalculate the duration.

d = Duration.between ( now , zdt ) ;

I ignored your desired ten minute gap, as I do not understand what you are doing there exactly, and it seems like a minor distraction. You can add ten minutes where needed along the process I outlined above.

CodePudding user response：

Based on your code you are checking if currentDay is from available list of days. If its not, then you are simply skipping your logic. I am suggesting you below --

for (DayOfWeek dayOfWeek : daysToFire) {
    if (currentDay == dayOfWeek) {

    final ZonedDateTime nextTime = currentZonedDateTime.with(TemporalAdjusters.nextOrSame(currentDay))
                            .withHour(hours).withMinute(mins).withSecond(0);
    
    if (nextTime.isAfter(currentZonedDateTime))
                        return Duration.between(currentZonedDateTime, nextTime);
      return Duration.between(nextTime, currentZonedDateTime);

    } else if (currentDay.getValue() < dayOfWeek.getValue()) {
                    final ZonedDateTime nextTime = currentZonedDateTime.with(TemporalAdjusters.nextOrSame(dayOfWeek))
                            .withHour(hours).withMinute(mins).withSecond(0);
                    return Duration.between(currentZonedDateTime, nextTime);
                } else
                    continue;
            }


  return Duration.ZERO;
}

Please let us know if this fulfils your requirement. Thanks.