* the user calls remove().)
         */
        return iterator.hasNext() || iterable.iterator().hasNext();
      }

      @Override
      @ParametricNullness
      public T next() {
        if (!iterator.hasNext()) {
          iterator = iterable.iterator();
          if (!iterator.hasNext()) {
            throw new NoSuchElementException();
          }
        }

    }

    @Override
    public boolean hasNext() {
      return !stack.isEmpty();
    }

    @Override
    public T next() {
      Iterator<T> itr = stack.getLast(); // throws NSEE if empty
      T result = checkNotNull(itr.next());
      if (!itr.hasNext()) {
        stack.removeLast();
      }
      Iterator<T> childItr = children(result).iterator();

    Iterator<Entry<K, Collection<V>>> entryIterator = unfiltered.asMap().entrySet().iterator();
    boolean changed = false;
    while (entryIterator.hasNext()) {
      Entry<K, Collection<V>> entry = entryIterator.next();
      K key = entry.getKey();
      Collection<V> collection = filterCollection(entry.getValue(), new ValuePredicate(key));
      if (!collection.isEmpty()

    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()
  }

  /**

    // known nonempty since we checked targets.size() > 1

    if (!thisIterator.hasNext()) {
      return false;
    }

    Object target = thatIterator.next();
    E current = thisIterator.next();
    try {
      while (true) {
        int cmp = unsafeCompare(current, target);

        if (cmp < 0) {
          if (!thisIterator.hasNext()) {
            return false;
          }

            Iterator<Exclusion> i1 = ce1.iterator();
            Iterator<Exclusion> i2 = ce2.iterator();
            while (i1.hasNext() && i2.hasNext()) {
                if (!equals(i1.next(), i2.next())) {
                    return false;
                }
            }
            return !i1.hasNext() && !i2.hasNext();
        }
        return false;
    }

    private boolean equals(Exclusion e1, Exclusion e2) {

    assertTrue(iterator.hasNext());
    assertEquals("1", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("2", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("3", iterator.next());
    assertTrue(iterator.hasNext());
    assertEquals("4", iterator.next());
    assertFalse(iterator.hasNext());
    try {
      iterator.next();

   * documentation).
   */
  public boolean isOrdered(Iterable<? extends T> iterable) {
    Iterator<? extends T> it = iterable.iterator();
    if (it.hasNext()) {
      T prev = it.next();
      while (it.hasNext()) {
        T next = it.next();
        if (compare(prev, next) > 0) {
          return false;
        }
        prev = next;
      }
    }
    return true;
  }

    public String toString() {
      return toString;
    }
  }

  Stimulus<E, Iterator<E>> hasNext =
      new Stimulus<E, Iterator<E>>("hasNext") {
        @Override
        void executeAndCompare(ListIterator<E> reference, Iterator<E> target) {
          assertEquals(reference.hasNext(), target.hasNext());
        }
      };
  Stimulus<E, Iterator<E>> next =
      new Stimulus<E, Iterator<E>>("next") {