Formatting a Duration in Java 8 / jsr310

Question

I am transitioning a project from Joda-Time to java8's native time libraries, and I have run into a snag.

I have been unable to find a formatter for Duration. I would like to have a custom String format of, for instance, HHH+MM, where a Duration of 75 hours and 15 minutes would format as "75+15".

This was easy to do with Joda-Time by converting to period, and using a PeriodFormatter, but I have been unable to find this type of class in Java8. Am I missing something?

Answer 1

Java 9 and later: Duration::to…Part methods

In Java 9 the Duration class gained new to…Part methods for returning the various parts of days, hours, minutes, seconds, milliseconds/nanoseconds. See this pre-release OpenJDK source code.

Given a duration of 49H30M20.123S…

• toNanosPart() = 123000000
• toMillisPart() = 123
• toSecondsPart() = 20
• toMinutesPart() = 30
• toHoursPart() = 1
• toDaysPart() = 2

Remember that “days” here means chunks of 24-hours, ignoring dates on a calendar. If you care about dates, use Period class instead.

I do not know if any additional formatter features are added. But at least you will be able to more conveniently generate your own strings from numbers obtained via these new getter methods.

Java 8

Oddly enough, no convenient getter methods for these values were included in the first edition release of java.time in Java 8. One of very few oversights in the otherwise excellent design of the java.time framework.

See the related Question: Why can't I get a duration in minutes or hours in java.time?.