How to add Business hours to Date considering not adding weekends ? - Java

Question

I want to add certain number of hours to date, ignoring the weekends

For example,

(Friday 18:00) + 48 = (Tuseday 18:00) (Saturday and Sunday are ignored)

Answer 1

I would strongly recommend using JodaTime (or DateTimeof Java8) for this, since the old Date/Calendar API is pretty useless.

public DateTime getEndtime(final DateTime startdate, final int hours) {
    final DateTime endOfWeek = endOfWeek(startdate);

    final Duration restOfWeek = new Duration(startdate, endOfWeek);

    final Duration hoursDuration = toDuration(hours);
    if (restOfWeek.isLongerThan(hoursDuration)) {
        return startdate.plus(hoursDuration);
    } else {
        final Duration durationForNextWeek = hoursDuration.minus(restOfWeek);
        return startOfWeek(startdate).plus(durationForNextWeek);
    }
}

//Converts number of hours as int to Duration
private Duration toDuration(final int hours) {
    return new Duration(hours * 60 * 60 * 1000);
}

//Returns coming friday, 1 millisecond to midnight
private DateTime endOfWeek(final DateTime dateTime) {
    DateTime copy = dateTime;
    while (copy.getDayOfWeek() != 6) {
        copy = copy.plusDays(1);
    }

    return copy.toDateMidnight().toDateTime().minusMillis(1);
}

//Returns the following monday at midnight
//If dateTime is on a monday, the next monday will be chosen
private DateTime startOfWeek(final DateTime dateTime) {
    DateTime copy = dateTime.plusDays(1);
    while (copy.getDayOfWeek() != 1) {
        copy = copy.plusDays(1);
    }

    return copy.toDateMidnight().toDateTime();
}

Explanation of the code:

• Check whether the number of hours can be added without crossing into a weekend
• If no, just add the hours to the startdate
• If yes, find the duration to be transferred to the next week, and add it to the start of the week

This code NOT support tasks stretching over multiple weeks, but it's a start that you can modify to support this.. Might be some edge cases that aren't handled as well, I'll leave it to you to test it thoroughly.