Convert a Java Future to a Scala Future

Question

I have a Java Future object which I would like to convert into a Scala Future.

Looking at the j.u.c.Future API, there is nothing much that I could use other than the isDone method. Is this isDone method blocking?

Currently this is what I have in my mind:

val p = Promise()
if (javaFuture.isDone())
  p.success(javaFuture.get)

Is there a better way to do this?

Answer 1

Starting Scala 2.13, the standard library includes scala.jdk.FutureConverters which provides Java to Scala CompletableFuture/Future implicit conversions:

import scala.jdk.FutureConverters._

// val javaFuture = java.util.concurrent.CompletableFuture.completedFuture(12)
val scalaFuture = javaFuture.asScala
// scalaFuture: scala.concurrent.Future[Int] = Future(Success(12))