val serverActor: ActorSystem[EchoMsg] = ActorSystem(ServerActor(), "serverActor")
val resultFuture = serverActor ? (replyTo => EchoMsg(str, replyTo))
val resultFuture = serverActor.ask(EchoMsg(str, _))
replyTo 系统自动创建
Actor[akka://serverActor/temp/user$a#0]
Actor[akka://serverActor/temp/user$b#0]



关键日志信息
server receive msg hello,sender=Actor[akka://serverActor/temp/user$a#0],self=Actor[akka://serverActor/user#0]
EchoMsg(hello,Actor[akka://serverActor/user#0])

server receive msg akka,sender=Actor[akka://serverActor/temp/user$b#0],self=Actor[akka://serverActor/user#0]
EchoMsg(akka,Actor[akka://serverActor/user#0])

server receive msg typed,sender=Actor[akka://serverActor/temp/user$c#0],self=Actor[akka://serverActor/user#0]
EchoMsg(typed,Actor[akka://serverActor/user#0])

/             根
/system       系统创建
/user         用户创建  ActorSystem.actorOf 
/deadLetters 
/temp         系统创建 用于实现 ActorRef.ask
/remote       远程引用

/deadLetters 的一个例子见
 akka actor ask 模式 实例 


完整代码
https://gitee.com/dyyx/hellocode/blob/master/demo/scala/akka/akka-quickstart-scala-maven/src/main/java/com/example/ask/EchoTypedActorAskDemo.scala


package com.example.ask

import akka.actor.typed.scaladsl.AskPattern.Askable
import akka.actor.typed.scaladsl.Behaviors
import akka.actor.typed.{ActorRef, ActorSystem, Behavior}
import akka.util.Timeout

import java.util.concurrent.TimeUnit
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.Success

final case class EchoMsg(msg: String, sender: ActorRef[EchoMsg])

object ServerActor {
  def apply(): Behavior[EchoMsg] = Behaviors.receive { (context, message) =>
    println("server receive msg " + message.msg + ",sender=" + message.sender + ",self=" + context.self)
    Thread.sleep(500)
    message.sender ! EchoMsg(message.msg, context.self)
    Behaviors.same
  }
}

object EchoTypedActorMain extends App {

  val serverActor: ActorSystem[EchoMsg] = ActorSystem(ServerActor(), "serverActor")
  val list = List("hello", "akka", "typed", "actor")

  implicit private val timeout: Timeout = Timeout(1, TimeUnit.SECONDS)
  implicit private val scheduler = serverActor.scheduler

  list.foreach { str =>
    val resultFuture = serverActor ? (replyTo => EchoMsg(str, replyTo))
    resultFuture.onComplete {
      case Success(value) => println(value)
    }
    println()
    Thread.sleep(1000)
  }


  list.foreach { str =>
    val resultFuture = serverActor.ask(EchoMsg(str, _))
    resultFuture.onComplete {
      case Success(value) => println(value)
    }
    println()
    Thread.sleep(1000)
  }
}