Scala example source code file (chameneos.scala)

This example Scala source code file (chameneos.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

blue, blue, colour, colour, creature, faded, int, list, meetingplace, red, red, yellow, yellow, yellow,yellow

The Scala chameneos.scala source code

/* The Computer Language Shootout
   http://shootout.alioth.debian.org/
   contributed by Yura Taras
   modified by Isaac Gouy
*/


object chameneos {
  abstract class Colour 
  case object RED extends Colour
  case object YELLOW extends Colour
  case object BLUE extends Colour
  case object FADED extends Colour
  val colours = List(RED, BLUE, YELLOW, FADED)
  class MeetingPlace(var n: Int) {
    var other: Creature = _
    def meet(c: Creature) = synchronized {
      if(n > 0) {
          if(other == null) {
            other = c;
            this.wait()
          } else {
            other.setOther(c.colour)
            c.setOther(other.colour)
            other = null
            n = n - 1
            this.notify()
          }
        } else {
          c.setOther(FADED)
      }
    }
  }
  class Creature(private val mp: MeetingPlace, var colour: Colour) extends Thread {
    private var met = 0
    var other: Colour = _
    def setOther(_o: Colour) {
      other = _o
    }
    def getCreaturesMet = met
    override def run() {
      try {
        while(colour != FADED) {
          mp.meet(this)
          if(other == FADED) {
            colour = FADED
          } else {
            met = met + 1
            colour = complement(other)
          }
        }
      } catch {
        case e:InterruptedException => () // Let the thread exit
      }
    }
    
    def complement(other: Colour) = (colour, other) match {
      case (RED, YELLOW)   => BLUE
      case (RED, BLUE)     => YELLOW
      case (RED, RED)      => RED
      case (YELLOW, BLUE)  => RED
      case (YELLOW, RED)   => BLUE
      case (YELLOW,YELLOW) => YELLOW
      case (BLUE, RED)     => YELLOW
      case (BLUE, YELLOW)  => RED
      case (BLUE, BLUE)    => BLUE
      case (FADED, _)      => FADED
    }
  }
  
  def apply(n: Int) {
      val mp = new MeetingPlace(n)
      val creatures = for(x <- colours) yield {
        val cr = new Creature(mp, x);
        cr.start();
        cr
      }
      creatures.foreach(x => x.join)
      val meetings = (creatures foldLeft 0) {(x, y) => (x + y.getCreaturesMet)}
      Console.println(meetings)
  }

  def main(args: Array[String]) {
    if(args.length < 1) throw new IllegalArgumentException();
    chameneos(Integer.parseInt(args(0)))
  }
}