Akka actors take the stage

Akka is a Scala library, which let's us implement the message-based concurrency systems. An actor is like a small program with a message queue of its own. You can only get an actor to do some work by passing it a message.

Here is our FileFinder object as an actor:

import akka.actor._
import akka.util.Timeout
import scala.io.Source

object FileFinder { // 1
  def props() = Props(new FileFinder)
  case class FileFinderMsg(pat: String, rootDir: String)
}

class FileFinder extends Actor { // 2 
  import FileFinder._
  import context._
  import java.io.File

  val grepActor = system.actorOf(Props(new GrepAFile), ""GrepAFile"") // 3

  def recurseIntoDir(dir: File): Iterable[File] = { // 4
    val itsChildren = new Iterable[File] {
      def iterator = if (dir.isDirectory) dir.listFiles.iterator else Iterator.empty
    }
    Seq(dir) ++: itsChildren.flatMap(recurseIntoDir(_))
  }

  def receive = { // 5
    case FileFinderMsg(pat, rootDir) => {
      val d = new File...