SynchronizedExample.scala

/* proof of concept for non atomic method */
/* to fix this the call should be wrapped */
/* inside a synchronized block */

private var uidCount = 0L

def getUniqueId(): Long = {
 uidCount = uidCount + 1
 uidCount
}
/* wrap the insecure function in a thread */
def startThread() = {
  val t = new Thread {
    override def run() {
      val uids =
      for (i <- 0 until 10) yield getUniqueId()
      println(uids)
    }
  }
  t.start()
  t
}  

/* fixed version */

val x = new AnyRef {}

def getUniqueIdSync(): Long = x.synchronized {
 uidCount = uidCount + 1
 uidCount
}

def startSyncThread() = {
  val t = new Thread {
    override def run() {
      val uids =
      for (i <- 0 until 10) yield getUniqueId()
      println(uids)
    }
  }
  t.start()
  t
}