*     queue, false if the associated FinalizableReferenceQueue is no longer referenced.
   */
  private boolean cleanUp(Reference<?> firstReference) {
    Method finalizeReferentMethod = getFinalizeReferentMethod();
    if (finalizeReferentMethod == null) {
      return false;
    }

    if (!finalizeReference(firstReference, finalizeReferentMethod)) {
      return false;
    }

    /*