* supplied {@code Future} is done, unless this {@code Future} has already been cancelled or set
   * (including "set asynchronously," defined below).
   *
   * <p>If the supplied future is {@linkplain #isDone done} when this method is called and the call
   * is accepted, then this future is guaranteed to have been completed with the supplied future by

    // TODO(kevinb): The descendingMap is never actually cached at all. Either:
    //
    // - Cache it, and annotate the field with @LazyInit.
    // - Simplify the code below, and consider eliminating the field (b/287198172), which is also
    //   set by one of the constructors.
    ImmutableSortedMap<K, V> result = descendingMap;
    if (result == null) {
      if (isEmpty()) {

   *   Iterator<E> it = set2.descendingIterator();
   *   while (it.hasNext())
   *     foo(it.next());
   *   }
   * }
   * }</pre>
   *
   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>The returned navigable set will be serializable if the specified navigable set is
   * serializable.
   *

   * that entries are indexable using ints.
   */
  static final int MAXIMUM_CAPACITY = Ints.MAX_POWER_OF_TWO;

  /** The maximum number of segments to allow; used to bound constructor arguments. */
  static final int MAX_SEGMENTS = 1 << 16; // slightly conservative

  /** Number of (unsynchronized) retries in the containsValue method. */

   *   Iterator<V> i = values.iterator(); // Must be in synchronized block
   *   while (i.hasNext()) {
   *     foo(i.next());
   *   }
   * }
   * }</pre>
   *
   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>Note that the generated multimap's {@link Multimap#removeAll} and {@link
   * Multimap#replaceValues} methods return collections that aren't synchronized.

  }

  public void testToStringWithNull() {
    Iterator<@Nullable String> iterator =
        Lists.<@Nullable String>newArrayList("hello", null, "world").iterator();
    assertEquals("[hello, null, world]", Iterators.toString(iterator));
  }

  public void testToStringEmptyIterator() {
    Iterator<String> iterator = Collections.<String>emptyList().iterator();

   * strong values, and no automatic eviction of any kind.
   *
   * <p>Note that while this return type is {@code CacheBuilder<Object, Object>}, type parameters on
   * the {@link #build} methods allow you to create a cache of any key and value type desired.
   */
  public static CacheBuilder<Object, Object> newBuilder() {
    return new CacheBuilder<>();
  }

  /**

      return collectTypes(ImmutableList.of(type));
    }

    ImmutableList<K> collectTypes(Iterable<? extends K> types) {
      // type -> order number. 1 for Object, 2 for anything directly below, so on so forth.
      Map<K, Integer> map = Maps.newHashMap();
      for (K type : types) {
        collectTypes(type, map);
      }
      return sortKeysByValue(map, Ordering.natural().reverse());
    }

    /* The iterator currently returning elements. */
    private Iterator<? extends T> iterator;

    /*
     * We track the "meta iterators," the iterators-of-iterators, below.  Usually, topMetaIterator
     * is the only one in use, but if we encounter nested concatenations, we start a deque of
     * meta-iterators rather than letting the nesting get arbitrarily deep.  This keeps each