Converts from a scala.concurrent.Future to a java.util.concurrent.Future

scala-future-to-java-future.scala

import scala.util._
import scala.concurrent._
import java.util.concurrent.{Callable, FutureTask}

object Utils {
  def toJavaFuture[TScalaType, TJavaType](f: Future[TScalaType])(map: (TScalaType => TJavaType))(implicit executor: ExecutionContext): java.util.concurrent.Future[TJavaType] = {
    val applied = f.map(map)

    val task = new FutureTask[TJavaType](new Callable[TJavaType] {
      def call(): TJavaType = applied.value.get match {
        case Success(v) => v
        case Failure(t) => throw new ExecutionException(s"Failure during execution", t)
        case _ => throw new ExecutionException(s"Failure during execution", null)
      }
    })

    applied.onComplete {
      case _ =>
        task.run()
    }

    task
  }
}