thrownAtomicReferenceFieldUpdaterFailure = atomicReferenceFieldUpdaterFailure;
          helper = new SynchronizedHelper();
        }
      }
    } else {
      /*
       * We avoid Unsafe, since newer JVMs produce warnings or even errors for attempts to use it.
       *
       * In guava-jre, we avoid Unsafe by using VarHandle instead. But if we have references to

   * are used from Java 9 or higher (i.e., high enough to trigger the VarHandle code path), such a
   * lookup would fail with an IllegalAccessException. That may then trigger use of Unsafe (possibly
   * with a warning under recent JVMs), or it may fall back even further to
   * AtomicReferenceFieldUpdaterAtomicHelper, which would fail with a similar problem to
   * VarHandleAtomicHelperMaker, forcing us all the way to SynchronizedHelper.
   *

  // safely publish these objects and we won't need this whole discussion.
  // TODO(user,lukes): consider adding volatile to all these fields since in current known JVMs
  // that should resolve the issue. This comes at the cost of adding more write barriers to the
  // implementations.

  private Futures() {}

  /**