A StripedExecutor in Scala using only JDK primitives, to serialize execution per stripe

StripedExecutor.scala

// ©2012 Viktor Klang
// 4,192 bytes jarred

package java.klang

import java.util.concurrent. { Executor, ConcurrentHashMap, ConcurrentLinkedQueue }
import java.util.concurrent.atomic. { AtomicBoolean }
import scala.annotation.tailrec

trait Striped {
  self: Runnable =>
  def stripeId: AnyRef
}

class StripedExecutor(val parent: Executor) extends Executor {
    private val stripes = new ConcurrentHashMap[AnyRef, AnyRef]
    
    override final def execute(runnable: Runnable): Unit = {
      runnable match {
        case r: Striped with Runnable => executeStripe(r, r.stripeId)
        case other => parent execute other
      }
    }

    private def executeStripe(runnable: Runnable, stripe: AnyRef): Unit = (stripe match {
      case null => parent
      case stripe =>
        (stripes get stripe) match {
          case e: ExecutorStripe => e
          case null =>
            val newExecutorStripe = new ExecutorStripe(parent)
            stripes.putIfAbsent(stripe, newExecutorStripe) match {
              case null => newExecutorStripe
              case existing: ExecutorStripe => existing
            }
        }
    }) execute runnable
}

class ExecutorStripe(private val parent: Executor) extends ConcurrentLinkedQueue[Runnable] with Runnable with Executor {
  private val scheduled = new AtomicBoolean(false)

    final override def execute(runnable: Runnable): Unit = {
      assert(offer(runnable))
      trySchedule()
    }

  final override def run = try {
      @tailrec def runNext(): Unit = poll match {
        case null =>
          ()
        case some =>
          some.run()
          runNext()
      }

      runNext()
  } finally {
    scheduled.set(false)
    trySchedule()
  }

  private final def trySchedule(): Unit = {
    if (!isEmpty && scheduled.compareAndSet(false, true)) {
      try {
        parent execute this
      } catch {
        case e => scheduled.set(false); throw e
      }
    }
  }
}