Playing with futures in Scala

Zoo.scala

import scala.util.{ Failure, Success }
import scala.concurrent.{ Future }
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global
import math.random

object Zoo extends App {

  val animals = List("monkey", "donkey", "giraffe").map { animal =>
    for { 
      fed <- feed(animal)
      washedAndFed <- wash(fed)
    } yield washedAndFed
  }

  def feed(animal: String) = Future {
    Thread.sleep(150) // take some time
    animal
  }
  
  def wash(animal: String) = Future {
    Thread.sleep(250) // take some time
    if ((random * 100).toInt > 75) throw new Exception // the animal got angry
    else animal
  }
  
  val cleanedAndFedAnimals = Future.sequence(animals)
  
  cleanedAndFedAnimals onComplete {
    case Success(res) => println("Happy animals: " + res.mkString(", "))
    case Failure(_) => println("Sad zookeeper :(")
  }
  
  Thread.sleep(500)
}