在Akka经典Ask模式中，Actor使用ask方法发送消息并等待响应。 ask方法将Future对象作为返回值，该对象包含接收到的响应消息。以下是一个示例，其中Actor1向Actor2发送一个字符串消息，Actor2返回大写的字符串响应消息。

Actor1代码：

import akka.actor.Actor
import akka.pattern.ask
import akka.util.Timeout
import scala.concurrent.Future
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global

class Actor1 extends Actor {
  implicit val timeout: Timeout = Timeout(5.seconds)
  val actor2 = context.actorOf(Actor2.props)
  
  override def receive: Receive = {
    case message: String =>
      val response: Future[String] = (actor2 ? message).mapTo[String]
      response.onComplete { 
        case scala.util.Success(res) => println(s"Actor1 received response: $res")
        case scala.util.Failure(t) => println(s"Actor1 received failure: $t")
      }
  }
}

Actor2代码：

import akka.actor.{Actor, Props}

class Actor2 extends Actor {
  override def receive: Receive = {
    case message: String => 
      val response = message.toUpperCase
      sender() ! response
  }
}

object Actor2 {
  def props: Props = Props[Actor2]
}

在Actor1中，使用ask方法发送字符串消息并等待响应，响应将被映射到Future String，并在onComplete回调函数中处理响应或失败。在Actor2中，接收到字符串消息后，将该消息转换为大写，并使用sender()方法将响应消息发送回Actor1。