WaitingWithRetryUsingScalaSTM.groovy

@Grab('org.scala-stm:scala-stm_2.10:0.7')
import scala.concurrent.stm.TxnUnknown$
import static scala.concurrent.stm.japi.STM.*
import static scala.concurrent.stm.Txn.*

void retry() {
  def txn = findCurrent(TxnUnknown$.MODULE$).get()
  retry(txn)
}

def x = newRef(0)

Thread.start {
  println "bg thread sleeping"
  sleep 2000
  println "changing x"
  x.set(1)
}

atomic {
  if (x.get() == 0) retry()
}

println "waiting finished"

Groovy version of https://gist.github.com/anonymous/2516410
You could of course keep more of the variable typing information if you wanted.