Problem with Java 7 UUID.random()

MultithreadedUniquenessOfUUID.scala

package com.automatak.archivist.server.uuid

import org.scalatest.FunSuite
import org.scalatest.matchers.ShouldMatchers
import org.scalatest.junit.JUnitRunner
import org.junit.runner.RunWith

import com.automatak.commons.testing._
import java.util.UUID

@RunWith(classOf[JUnitRunner])
class MutlithreadedUniquenessOfUUID extends FunSuite with ShouldMatchers {

  test("Warm up the generator") {
    1000000.times(UUID.randomUUID())
  }

  test("Highly concurrently generated UUIDS are still unique") {

    val uuidPerThread = 100000
    val numThreads = 64
    val totalUUID = uuidPerThread * numThreads

    val set = collection.mutable.Set.empty[UUID]

    val threads = numThreads create {
      onAnotherThread {
        uuidPerThread times {
          val uuid = UUID.randomUUID()
          set.synchronized {
            if (set.contains(uuid)) println(uuid)
            else set += uuid
          }
        }
      }
    }

    val (ns, _) = time(threads.foreach(_.join()))

    set.size should equal(totalUUID)
  }

}