ตัวอย่างการใช้งาน Future ใน Scala อย่างง่าย และการสร้าง ExecutionContext

FutureExample.scala

package example

import scala.concurrent.duration.Duration
import scala.concurrent.{ Future, Await }
//import scala.concurrent.ExecutionContext.Implicits.global

object Hello extends Greeting with App {
  Prog.debug("Starting Main")
  val futureA = Prog.taskA()
  val futureB = Prog.taskB()
  Prog.debug("Finished Main")
  Await.result(futureA zip futureB, Duration.Inf)
}

object Prog {

  /*implicit*/ val executor =  scala.concurrent.ExecutionContext.global

  def taskA(): Future[Unit] = Future {
    debug("Starting taskA")
    Thread.sleep(1000) // wait 1secs
    debug("Finished taskA")
  } (executor)

  def taskB(): Future[Unit] = Future {
    debug("Starting taskB")
    Thread.sleep(2000) // wait 2secs
    debug("Finished taskB")
  } (executor)

  def debug(message: String): Unit = {
    val now = java.time.format.DateTimeFormatter.ISO_INSTANT
      .format(java.time.Instant.now)
      .substring(11, 23) // keep only time component
    val thread = Thread.currentThread.getName()
    println(s"$now [$thread] $message")
  }
}