Duration

§Finite vs. Infinite

Since trying to convert an infinite duration into a concrete time unit like seconds will throw an exception, there are different types available for distinguishing the two kinds at compile time:

• FiniteDuration is guaranteed to be finite, calling toNanos and friends is safe
• Duration can be finite or infinite, so this type should only be used when finite-ness does not matter; this is a supertype of FiniteDuration

§Scala

In Scala durations are constructable using a mini-DSL and support all expected arithmetic operations:

import scala.concurrent.duration._
 
val fivesec = 5.seconds
val threemillis = 3.millis
val diff = fivesec - threemillis
assert(diff < fivesec)
val fourmillis = threemillis * 4 / 3 // you cannot write it the other way around
val n = threemillis / (1 millisecond)

§Java

Java provides less syntactic sugar, so you have to spell out the operations as method calls instead:

import scala.concurrent.duration.Duration;
import scala.concurrent.duration.Deadline;

final Duration fivesec = Duration.create(5, "seconds");
final Duration threemillis = Duration.create("3 millis");
final Duration diff = fivesec.minus(threemillis);
assert diff.lt(fivesec);
assert Duration.Zero().lt(Duration.Inf());

§Deadline

Durations have a brother named Deadline, which is a class holding a representation of an absolute point in time, and support deriving a duration from this by calculating the difference between now and the deadline. This is useful when you want to keep one overall deadline without having to take care of the book-keeping wrt. the passing of time yourself:

val deadline = 10.seconds.fromNow
// do something
val rest = deadline.timeLeft

In Java you create these from durations:

final Deadline deadline = Duration.create(10, "seconds").fromNow();
final Duration rest = deadline.timeLeft();