exploring-scala-2

CommonsCollections.scala

object Colecoes extends Application {
  val myList = List.range(-5, 5)

  CollectionUtils.forAllDo(
    CollectionUtils.collect(
      CollectionUtils.select(myList,
        new Predicate() {
          def evaluate(obj: Object): Boolean =
            return obj.asInstanceOf[Int] > 0;
        }), new Transformer() {
        def transform(obj: Object): Object = {
          return (2 * obj.asInstanceOf[Int])
            .asInstanceOf[Object];
        }
      }),
    new Closure() {
      def execute(obj: Object) {
        println(obj);
      }
    })
}

ParCol.scala

object ParCol{
  def main(args: Array[String]) {
    (1 to 5).foreach(println);
    (1 to 5).par.foreach(println); 
  }
}

PiCalculator.scala

case object Calculate
case object ShutDown

class Calculator extends Actor {
  val rand = new Random
  var pi, in, cnt = 1.0

  def act() {
    while (true) {
      receive {
        case Calculate =>
          sender ! estimativeOfPi
        case ShutDown => exit
      }
    }
  }

  def estimativeOfPi: Double = {
    val x = rand.nextDouble - 0.5
    val y = rand.nextDouble - 0.5
    cnt += 1.0;
    if (sqrt(x * x + y * y) < 0.5) in += 1
    return in / cnt * 4
  }
}

PiCoordinator.scala

class Coordinator(numOfCalculators: Int) extends Actor {
  def act() {
    val startedAt = currentTimeMillis
    var calculators = List.fill(numOfCalculators)(new Calculator)
    calculators.foreach(c => {
        c.start
        c ! Calculate
    })
    while (true) {
      receive {
        case estimative: Double =>
          val error = abs(Pi - estimative)
          if (error > 0.0000001)
            sender ! Calculate
          else {
            val tempo = currentTimeMillis - startedAt
            calculators.foreach(_ ! ShutDown)                        
            println("Pi found by " + sender + " = " + estimative)
            println("Execution time: " + tempo)
            exit
          }
      }
    }
  }
}

PiMain.scala

object PiActors {
  def main(args: Array[String]) {
    new Coordinator(2).start
  }
}

PrintParametersServlet.scala

@WebServlet(Array("/mostraParams"))
class PrintParametersServlet extends HttpServlet {
  override def doGet(req: HttpServletRequest,
    resp: HttpServletResponse) {  
    val out = resp.getWriter();
    req.getParameterMap()
      .map {case (key, value) => key +" = "+ value.mkString(",")}
      .foreach(out.println(_))
  }
}

ScalaCollections.scala

myList.filter(_ > 0).map(_ * 2).foreach(println(_));