Scala example source code file (auction.scala)

This example Scala source code file (auction.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

actor, actor, auctionconcluded, auctionmessage, auctionover, auctionreply, auctionreply, beatenoffer, date, int, int, offer, offer, timeout, util

The Scala auction.scala source code

package examples.actors

import java.util.Date

import scala.actors._
import scala.actors.Actor._

/** A simple demonstrator program implementing an online auction service
 *  The example uses the actor abstraction defined in the API of
 *  package scala.actors.
 */

trait AuctionMessage
case class Offer(bid: Int, client: Actor) extends AuctionMessage // make a bid
case class Inquire(client: Actor) extends AuctionMessage         // inquire status

trait AuctionReply
case class Status(asked: Int, expiration: Date)           // asked sum, expiration date
  extends AuctionReply
case object BestOffer extends AuctionReply                // yours is the best offer
case class BeatenOffer(maxBid: Int) extends AuctionReply  // offer beaten by maxBid
case class AuctionConcluded(seller: Actor, client: Actor) // auction concluded
  extends AuctionReply
case object AuctionFailed extends AuctionReply            // failed with no bids
case object AuctionOver extends AuctionReply              // bidding is closed

class AuctionActor(seller: Actor, minBid: Int, closing: Date) extends Actor {
  val timeToShutdown = 3000 // msec
  val bidIncrement = 10

  def act() {
    var maxBid = minBid - bidIncrement
    var maxBidder: Actor = null

    loop {
      reactWithin (closing.getTime() - new Date().getTime()) {

        case Offer(bid, client) =>
          if (bid >= maxBid + bidIncrement) {
            if (maxBid >= minBid)
              maxBidder ! BeatenOffer(bid)
            maxBid = bid
            maxBidder = client
            client ! BestOffer
          }
          else
            client ! BeatenOffer(maxBid)

        case Inquire(client) =>
          client ! Status(maxBid, closing)

        case TIMEOUT =>
          if (maxBid >= minBid) {
            val reply = AuctionConcluded(seller, maxBidder)
            maxBidder ! reply
            seller ! reply
          } else {
            seller ! AuctionFailed
          }
          reactWithin(timeToShutdown) {
            case Offer(_, client) => client ! AuctionOver
            case TIMEOUT => exit()
          }

      }
    }
  }
}

object auction {

  val random = new scala.util.Random

  val minBid = 100
  val closing = new Date(new Date().getTime() + 4000)

  val seller = Actor.actor { }
  val auction = new AuctionActor(seller, minBid, closing)

  def client(i: Int, increment: Int, top: Int) = new Actor {
    val name = "Client " + i
    def log(msg: String) = Console.println(name + ": " + msg)
    var max: Int = _
    var current: Int = 0
    def act() {
      log("started")
      auction ! Inquire(this)
      receive {
        case Status(maxBid, _) =>
          log("status(" + maxBid + ")")
          max = maxBid
      }
      loop {
        if (max >= top) {
          log("too high for me")
        }
        else if (current < max) {
          current = max + increment
          Thread.sleep(1 + random.nextInt(1000))
          auction ! Offer(current, this)
        }

        reactWithin(3000) {
          case BestOffer =>
            log("bestOffer(" + current + ")")

          case BeatenOffer(maxBid) =>
            log("beatenOffer(" + maxBid + ")")
            max = maxBid

          case AuctionConcluded(seller, maxBidder) =>
            log("auctionConcluded"); exit()

          case AuctionOver =>
            log("auctionOver"); exit()

          case TIMEOUT =>
            exit()
        }
      }
    }
  }

  def main(args: Array[String]) {
    seller.start()
    auction.start()
    client(1, 20, 200).start()
    client(2, 10, 300).start()
  }

}