for (T input : inputs) {
          collector.accumulator().accept(accum, input);
        }
        return accum;
      }
    },
    /** Get one accumulator for each element and merge the accumulators left-to-right. */
    MERGE_LEFT_ASSOCIATIVE {
      @Override
      final <T extends @Nullable Object, A extends @Nullable Object, R extends @Nullable Object>
          A result(Collector<T, A, R> collector, Iterable<T> inputs) {

/**
 * A future whose value is derived from a collection of input futures.
 *
 * @param <InputT> the type of the individual inputs
 * @param <OutputT> the type of the output (i.e. this) future
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AggregateFuture<InputT extends @Nullable Object, OutputT extends @Nullable Object>
    extends AggregateFutureState<OutputT> {

    }

    void assertHasImmediateCancel(
        ListenableFuture<String> a, ListenableFuture<String> b, Exception e) {
      ImmutableSet<ListenableFuture<String>> inputs = ImmutableSet.of(a, b);
      smartAssertTrue(inputs, e, intersect(inputs, ImmutableSet.of(doneCancelled)));
    }
  }

  /**

      new Predicate<Integer>() {
        @Override
        public boolean apply(Integer input) {
          return input % 2 == 0;
        }
      };

  private static final Predicate<Integer> PRIME_DIGIT = Predicates.in(ImmutableSet.of(2, 3, 5, 7));

  private static final ImmutableList<? extends List<Integer>> SAMPLE_INPUTS =
      ImmutableList.of(
          ImmutableList.<Integer>of(),
          ImmutableList.of(1),

    }

    void assertHasImmediateCancel(
        ListenableFuture<String> a, ListenableFuture<String> b, Exception e) {
      ImmutableSet<ListenableFuture<String>> inputs = ImmutableSet.of(a, b);
      smartAssertTrue(inputs, e, intersect(inputs, ImmutableSet.of(doneCancelled)));
    }
  }

  /**

    /*
     * TODO: cpovirk - Pre-size the HashMap based on the number of enum values? (But *not* based on
     * the number of entries in the map, as that makes it easy for hostile inputs to trigger lots of
     * allocation—not that any program should be deserializing hostile inputs to begin with!)
     */
    setDelegates(new EnumMap<K, V>(keyTypeOrObjectUnderJ2cl), new HashMap<V, K>());
    Serialization.populateMap(this, stream);
  }

   * identical inputs: This sounds like it ought to be a problem here, since the goals of this class
   * include testing that {@code equals()} is reflexive and is tolerant of {@code null}. However,
   * there's no problem. The reason: {@link EqualsTester} tests {@code null} and identical inputs
   * directly against {@code equals()} rather than through the {@code Equivalence}.
   */

  }

  private static void assertMessageDigestHashing(byte[] input, String algorithmName) {
    try {
      MessageDigest digest = MessageDigest.getInstance(algorithmName);
      assertEquals(
          HashCode.fromBytes(digest.digest(input)), ALGORITHMS.get(algorithmName).hashBytes(input));
      for (int bytes = 4; bytes <= digest.getDigestLength(); bytes++) {
        assertEquals(

     *
     * Unfortunately, we don't distinguish between these two cases in our public API: Joiner.on(...)
     * and Joiner.on(...).useForNull(...) both declare the same return type: plain Joiner. To ensure
     * that users *can* pass null arguments to Joiner, we annotate it as if it always tolerates null
     * inputs, rather than as if it never tolerates them.
     *

  private static void assertMacHashing(
      byte[] input, String algorithm, SecretKey key, HashFunction hashFunc) throws Exception {
    Mac mac = Mac.getInstance(algorithm);
    mac.init(key);
    mac.update(input);

    assertEquals(HashCode.fromBytes(mac.doFinal()), hashFunc.hashBytes(input));
    assertEquals(HashCode.fromBytes(mac.doFinal(input)), hashFunc.hashBytes(input));
  }