*
 * <p>An instance of this class is serializable if its reference is absent or is a serializable
 * object.
 *
 * <p><b>Comparison to {@code java.util.Optional} (JDK 8 and higher):</b> A new {@code Optional}
 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the

    return super.values();
  }

  @VisibleForTesting
  @WeakOuter
  final class ValueSet extends Sets.ImprovedAbstractSet<V> {
    /*
     * We currently use a fixed load factor of 1.0, a bit higher than normal to reduce memory
     * consumption.
     */

    @ParametricNullness private final K key;
    @VisibleForTesting @Nullable ValueEntry<K, V>[] hashTable;
    private int size = 0;

    return super.values();
  }

  @VisibleForTesting
  @WeakOuter
  final class ValueSet extends Sets.ImprovedAbstractSet<V> {
    /*
     * We currently use a fixed load factor of 1.0, a bit higher than normal to reduce memory
     * consumption.
     */

    @ParametricNullness private final K key;
    @VisibleForTesting @Nullable ValueEntry<K, V>[] hashTable;
    private int size = 0;

                        content_title:
                          type: string
                          example: "Open Source Enterprise Search Server: Fess — Fe..."
                        digest:
                          type: string

        for (Thread thread : threads) {
            thread.join();
        }

        // Due to synchronized method, only one thread should reload
        // The count might be 2 (one initial + one reload) or slightly higher due to timing
        assertTrue(loadCount[0] <= 3, "Load count should be small due to synchronization");
    }

    }

    @Override
    public @Nullable E ceiling(@ParametricNullness E e) {
      return delegate.ceiling(e);
    }

    @Override
    public @Nullable E higher(@ParametricNullness E e) {
      return delegate.higher(e);
    }

    @Override
    public @Nullable E pollFirst() {
      throw new UnsupportedOperationException();
    }

    @Override

 * {@linkplain #identity() identity equivalence} and the {@linkplain #equals "equals" equivalence}.
 *
 * <p><b>For users targeting Android API level 24 or higher:</b> This class will eventually
 * implement {@code BiPredicate<T, T>} (as it does in the main Guava artifact), but we currently
 * target a lower API level. In the meantime, if you have support for method references you can use

 * <i>not</i> include cache contents, but only configuration.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/CachesExplained">caching</a> for a higher-level
 * explanation.
 *
 * @param <K> the most general key type this builder will be able to create caches for. This is
 *     normally {@code Object} unless it is constrained by using a method like {@link

 *
 * <p>An instance of this class is serializable if its reference is absent or is a serializable
 * object.
 *
 * <p><b>Comparison to {@code java.util.Optional} (JDK 8 and higher):</b> A new {@code Optional}
 * class was added for Java 8. The two classes are extremely similar, but incompatible (they cannot
 * share a common supertype). <i>All</i> known differences are listed either here or with the

   * AbstractFutureState's private fields. However, our open-source build uses `-source 8 -target
   * 8`, so the class files from that build can't express nestmates. Thus, when those class files
   * 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