// will be a definite performance hit to those users.
          thrownAtomicReferenceFieldUpdaterFailure = atomicReferenceFieldUpdaterFailure;
          helper = new SynchronizedHelper();
        }
      }
    } else {
      /*
       * We avoid Unsafe, since newer JVMs produce warnings or even errors for attempts to use it.
       *

          // will be a definite performance hit to those users.
          thrownAtomicReferenceFieldUpdaterFailure = atomicReferenceFieldUpdaterFailure;
          helper = new SynchronizedHelper();
        }
      }
    }
    ATOMIC_HELPER = helper;

    // Prevent rare disastrous classloading in first call to LockSupport.park.
    // See: https://bugs.openjdk.org/browse/JDK-8074773

 * and performant but introduces some testing difficulties. This test exercises the two fallback
 * strategies.
 *
 * <ul>
 *   <li>SafeAtomicHelper: uses Atomic FieldsUpdaters to implement synchronization
 *   <li>SynchronizedHelper: uses {@code synchronized} blocks for synchronization
 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AggregateFutureState} (and all of

    }
    checkHelperVersion(NO_VAR_HANDLE, "UnsafeAtomicHelper");
    checkHelperVersion(NO_UNSAFE, "AtomicReferenceFieldUpdaterAtomicHelper");
    checkHelperVersion(NO_ATOMIC_REFERENCE_FIELD_UPDATER, "SynchronizedHelper");

    // Then, run the actual tests under each alternative classloader:

    /*
     * Under Java 8, there is no need to test the no-VarHandle case here: It's already tested by the