Scala: "try-Await" to "Try-onComplete"

// 1. Suppose we've got a Future[T] and usual blocking code:
import java.time.LocalDateTime

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.{Await, Future}
import scala.concurrent.duration._
import scala.io.StdIn
import scala.language.postfixOps
import scala.util.control.NonFatal

object Main extends App {

  def f(x: Int, y: Int): Future[Int] = Future {
    println(LocalDateTime.now() + ": Start calculation!")
    Thread.sleep(3000)
    println(LocalDateTime.now() + ": Done calculation!")
    x / y
  }

  try {
    println(LocalDateTime.now() + ": Hello!")
    val resultFut = f(5, 2)
    val result = Await.result(resultFut, 5 seconds)
    println(LocalDateTime.now() + s": Result is $result")
  } catch {
    case e: ArithmeticException => System.err.println(s"Arithmetic err! $e")
    case NonFatal(e) => println(s"Error: $e")
  }

  println(LocalDateTime.now() + ": Press ENTER to finish!")
  StdIn.readLine()
  println(LocalDateTime.now() + ": Bye!")
}

        // Output:
        // 2018-01-17T22:21:46.561: Hello!
        // 2018-01-17T22:21:46.690: Start calculation!
        // 2018-01-17T22:21:49.690: Done calculation!
        // 2018-01-17T22:21:49.692: Result is 2
        // 2018-01-17T22:21:49.695: Press ENTER to finish!

        // 2018-01-17T22:21:52.840: Bye!

// 2. Now try to fail and ensure it works properly:
val resultFut = f(5, 0)

        // Output:
        // 2018-01-17T22:23:18.419: Hello!
        // 2018-01-17T22:23:18.543: Start calculation!
        // 2018-01-17T22:23:21.543: Done calculation!
        // Arithmetic err! java.lang.ArithmeticException: / by zero
        // 2018-01-17T22:23:21.549: Press ENTER to finish!

        // 2018-01-17T22:23:24.544: Bye!

// 3. Let's make it async!
println(LocalDateTime.now() + ": Hello!")
f(5, 2) onComplete {
  case Success(result) => println(LocalDateTime.now() + s": Result is $result")
  case Failure(e: ArithmeticException) => System.err.println(s"Arithmetic err! $e")
  case Failure(NonFatal(e)) => println(s"Error: $e")
}

        // Output (note the order of lines!):
        // 2018-01-17T22:26:25.523: Hello!
        // 2018-01-17T22:26:25.645: Press ENTER to finish!
        // 2018-01-17T22:26:25.645: Start calculation!
        // 2018-01-17T22:26:28.645: Done calculation!
        // 2018-01-17T22:26:28.645: Result is 2

        // 2018-01-17T22:26:30.726: Bye!

// 4. Let's check failures:
f(5, 0)

        // Output (note the order of lines!):
        // 2018-01-17T22:26:54.466: Hello!
        // 2018-01-17T22:26:54.603: Press ENTER to finish!
        // 2018-01-17T22:26:54.604: Start calculation!
        // 2018-01-17T22:26:57.604: Done calculation!
        // Arithmetic err! java.lang.ArithmeticException: / by zero

        // 2018-01-17T22:26:59.366: Bye!

// 5. Now what if we need to return a result? way #1: with 'transform' function:
object Main extends App {

  def f(x: Int, y: Int): Future[Int] = Future {
    println(LocalDateTime.now() + ": Start calculation!")
    Thread.sleep(3000)
    println(LocalDateTime.now() + ": Done calculation!")
    x / y
  }

  println(LocalDateTime.now() + ": Hello!")
  val strResult = f(5, 0) transform {
    case Success(result) => Success(LocalDateTime.now() + s": Result is $result")
    case Failure(e: ArithmeticException) => Success(s"Arithmetic err! $e")
    case Failure(NonFatal(e)) => Success(s"Error: $e")
  }

  strResult foreach println // prints a result as soon as Future finishes

  println(LocalDateTime.now() + ": Press ENTER to finish!")
  StdIn.readLine()
  println(LocalDateTime.now() + ": Bye!")
}

        // Output:
        // 2018-01-17T22:33:45.196: Hello!
        // 2018-01-17T22:33:45.333: Start calculation!
        // 2018-01-17T22:33:45.334: Press ENTER to finish!
        // 2018-01-17T22:33:48.333: Done calculation!
        // Arithmetic err! java.lang.ArithmeticException: / by zero

        // 2018-01-17T22:33:50.794: Bye!

// 6. And way #2: with 'map-recover' functions:
object Main extends App {

  def f(x: Int, y: Int): Future[Int] = Future {
    println(LocalDateTime.now() + ": Start calculation!")
    Thread.sleep(3000)
    println(LocalDateTime.now() + ": Done calculation!")
    x / y
  }

  println(LocalDateTime.now() + ": Hello!")
  val strResult = f(5, 0) map { result =>
    LocalDateTime.now() + s": Result is $result"
  } recover {
    case e: ArithmeticException => s"Arithmetic err! $e"
    case NonFatal(e) => s"Error: $e"
  }

  strResult foreach println // prints a result as soon as Future finishes

  println(LocalDateTime.now() + ": Press ENTER to finish!")
  StdIn.readLine()
  println(LocalDateTime.now() + ": Bye!")
}

        // Output:
        // 2018-01-17T22:34:42.673: Hello!
        // 2018-01-17T22:34:42.805: Start calculation!
        // 2018-01-17T22:34:42.807: Press ENTER to finish!
        // 2018-01-17T22:34:45.806: Done calculation!
        // Arithmetic err! java.lang.ArithmeticException: / by zero

        // 2018-01-17T22:34:47.059: Bye!