使用期货和Thread.sleep [英] Using futures and Thread.sleep

问题描述

通过执行此Scala代码，控制台中没有任何输出. (我不太了解发生了什么事

By executing this scala code, I don't have any output in the console. (I don't really understand what is happening)

如果我删除Console.println("Console.println OK!") =>一切都很好.

If I remove Console.println("Console.println OK!") => everything seems fine.

如果我删除Thread.sleep(2000) =>一切似乎都很好.

If I remove Thread.sleep(2000) => everything seems fine.

您对此有任何想法吗?非常感谢你！

Do you have any ideas about this ? Thank you very much!

Clément

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._
import scala.concurrent.{Await, Future}
import scala.language.postfixOps

object ScalaFuture {

  def main(args: Array[String]) {

    val f: Future[String] = Future {
      Thread.sleep(2000)
      "future value"
    }

    f.onSuccess {
      case s => {
        Console.println("Console.println OK!")
        System.out.println("System.out.println OK!")
      }
    }

    Await.ready(f, 60 seconds)
  }

}

推荐答案

您的等待正在等待将来完成，这在2秒后完成，但是它不等待onSuccess处理程序，该处理程序在另一个线程中执行(与将来类似)，但是在Await.ready(f, 60 seconds)之后，因此进程比您打印某些内容更早退出.要正确处理它-为onComplete创建新的未来:

Your await is waiting for future to complete, which is done after 2 seconds, but it doesn't wait for onSuccess handler, which executes in another thread (similar to future), but after Await.ready(f, 60 seconds), so process exits earlier than you print something. To process it correctly - create new future for onComplete:

val f: Future[String] = Future {
  Thread.sleep(2000)
  "future value"
}

val f2 = f map { s => 
    println("OK!")
    println("OK!")    
}

Await.ready(f2, 60 seconds)
println("exit")

Await.ready(f, ...)的结果:

exit
OK!
OK!

Await.ready(f2, ...)的结果:

OK!
OK!
exit

这篇关于使用期货和Thread.sleep的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！