@Override
    @CheckForNull
    public E floor(@ParametricNullness E e) {
      return delegate.floor(e);
    }

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

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

    @Override

    @Override
    NavigableSet<E> delegate() {
      return (NavigableSet<E>) super.delegate();
    }

    @Override
    @CheckForNull
    public E ceiling(E e) {
      synchronized (mutex) {
        return delegate().ceiling(e);
      }
    }

    @Override
    public Iterator<E> descendingIterator() {
      return delegate().descendingIterator(); // manually synchronized
    }

         * invoke interruptTask on any subsequent futures.
         */
        callInterruptTask = false;
      }
      // We call this before the listeners in order to avoid needing to manage a separate stack data
      // structure for them.  Also, some implementations rely on this running prior to listeners
      // so that the cleanup work is visible to listeners.

      // covariantly (and cannot be subclassed to add non-covariant uses).
      @SuppressWarnings("unchecked")
      PeekingImpl<T> peeking = (PeekingImpl<T>) iterator;
      return peeking;
    }
    return new PeekingImpl<>(iterator);
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this
   * @since 10.0
   */

 * href="https://www.javadoc.io/doc/com.github.ben-manes.caffeine/caffeine/latest/com.github.benmanes.caffeine/com/github/benmanes/caffeine/cache/CacheLoader.html">{@code
 * CacheLoader}</a>, etc.), so you can use Caffeine without needing to use any Guava types.
 * Caffeine's types are better than Guava's, especially for <a