How to format a duration in java? (e.g format H:MM:SS)

Question

I\'d like to format a duration in seconds using a pattern like H:MM:SS. The current utilities in java are designed to format a time but not a duration.

Answer 1

There's a fairly simple and (IMO) elegant approach, at least for durations of less than 24 hours:

DateTimeFormatter.ISO_LOCAL_TIME.format(value.addTo(LocalTime.of(0, 0)))

Formatters need a temporal object to format, so you can create one by adding the duration to a LocalTime of 00:00 (i.e. midnight). This will give you a LocalTime representing the duration from midnight to that time, which is then easy to format in standard HH:mm:ss notation. This has the advantage of not needing an external library, and uses the java.time library to do the calculation, rather than manually calculating the hours, minutes and seconds.