* A sensible definition of {@link #isEmpty} as {@code !iterator().hasNext}. If you override
   * {@link #isEmpty}, you may wish to override {@link #isEmpty} to forward to this implementation.
   * Alternately, it may be more efficient to implement {@code isEmpty} as {@code size() == 0}.
   *
   * @since 7.0
   */
  protected boolean standardIsEmpty() {
    return !iterator().hasNext();
  }

  /**

   * A sensible definition of {@link #isEmpty} as {@code !iterator().hasNext}. If you override
   * {@link #isEmpty}, you may wish to override {@link #isEmpty} to forward to this implementation.
   * Alternately, it may be more efficient to implement {@code isEmpty} as {@code size() == 0}.
   *
   * @since 7.0
   */
  protected boolean standardIsEmpty() {
    return !iterator().hasNext();
  }

  /**

    abstract T output(int index);

    @Override
    public boolean hasNext() {
      for (; index < enumConstants.length; index++) {
        if (counts[index] > 0) {
          return true;
        }
      }
      return false;
    }

    @Override
    public T next() {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      T result = output(index);

    }

    // If we have a routes left, use 'em.
    if (routeSelection?.hasNext() == true) return true

    // If we haven't initialized the route selector yet, assume it'll have at least one route.
    val localRouteSelector = routeSelector ?: return true

    // If we do have a route selector, use its routes.
    return localRouteSelector.hasNext()
  }

  /**

  public void testClear() {
    collection.clear();
    assertTrue("After clear(), a collection should be empty.", collection.isEmpty());
    assertEquals(0, collection.size());
    assertFalse(collection.iterator().hasNext());
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testClear_unsupported() {

   * <i>may</i> prevent removal of the most recent element via {@link #remove()}.
   *
   * @throws NoSuchElementException if the iteration has no more elements according to {@link
   *     #hasNext()}
   */
  @ParametricNullness
  E peek();

  /**
   * {@inheritDoc}
   *
   * <p>The objects returned by consecutive calls to {@link #peek()} then {@link #next()} are

   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  @Override
  public final T next() {
    if (nextOrNull == null) {
      throw new NoSuchElementException();
    }
    T oldNext = nextOrNull;

     */
    public EmptyIterator() {
    }

    @Override
    public void remove() {
        throw new ClUnsupportedOperationException("remove");
    }

    @Override
    public boolean hasNext() {
        return false;
    }

    @Override
    public T next() {
        throw new ClUnsupportedOperationException("next");
    }

        throw new ConcurrentModificationException();
      }
    }

    @Override
    public boolean hasNext() {
      checkForConcurrentModification();
      return entryIndex >= 0;
    }

    @Override
    @ParametricNullness
    public T next() {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      T result = result(entryIndex);
      toRemove = entryIndex;

    return new UnmodifiableIterator<V>() {
      final UnmodifiableIterator<Entry<K, V>> entryItr = map.entrySet().iterator();

      @Override
      public boolean hasNext() {
        return entryItr.hasNext();
      }

      @Override
      public V next() {
        return entryItr.next().getValue();
      }
    };
  }

  @Override
  public boolean contains(@Nullable Object object) {