}

  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();

  //
  // ...where "@JointlyNullable" is similar to @PolyNull but slightly different:
  //
  // - @PolyNull means "@Nullable or @Nonnull"
  //   (That would be unsound for an input Iterable<@Nullable Foo>. So, if we wanted to use
  //   @PolyNull, we would have to restrict this method to non-null <T>. But it has users who pass
  //   iterables with null elements.)
  //
  // - @JointlyNullable means "@Nullable or no annotation"

   * 1] < [1, 2] < [2]}.
   *
   * <p>Note that {@code Collections.reverseOrder(lexicographical(comparator))} is not equivalent to
   * {@code lexicographical(Collections.reverseOrder(comparator))} (consider how each would order
   * {@code [1]} and {@code [1, 1]}).
   */
  // Note: 90% of the time we don't add type parameters or wildcards that serve only to "tweak" the

  /**
   * Returns an unmodifiable view of the intersection of two multisets. In the returned multiset,
   * the count of each element is the <i>minimum</i> of its counts in the two backing multisets,
   * with elements that would have a count of 0 not included. The iteration order of the returned
   * multiset matches that of the element set of {@code multiset1}, with repeated occurrences of the
   * same element appearing consecutively.
   *

    throw new InvalidObjectException("Use SerializedForm");
  }

  // This class is never actually serialized directly, but we have to make the
  // warning go away (and suppressing would suppress for all nested classes too)
  private static final long serialVersionUID = 0;

  /**
   * Not supported. Use {@link #toImmutableSortedMap}, which offers better type-safety, instead.

   * values are merged using the specified merging function. If the merging function returns {@code
   * null}, then the collector removes the value that has been computed for the key thus far (though
   * future occurrences of the key would reinsert it).
   *
   * <p>Entries will appear in the encounter order of the first occurrence of the key.
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */

      // unpark even though the thread has already removed itself from the list. But even if we did
      // use a CAS, that race would still exist (it would just be ever so slightly smaller).
      Thread w = thread;
      if (w != null) {
        thread = null;
        LockSupport.unpark(w);
      }
    }
  }

  /**

   *
   * <p>If {@code expectedSize} is exactly the number of entries added to the builder before {@link
   * Builder#build} is called, the builder is likely to perform better than an unsized {@link
   * #builder()} would have.
   *
   * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
   * but not exactly, the number of entries added to the builder.
   *
   * @since 23.1
   */

   *   <li>{@code ImmutableList.of(2, "C")}
   * </ul>
   *
   * <p>The result is guaranteed to be in the "traditional", lexicographical order for Cartesian
   * products that you would get from nesting for loops:
   *
   * <pre>{@code
   * for (B b0 : sets.get(0)) {
   *   for (B b1 : sets.get(1)) {
   *     ...
   *     ImmutableList<B> tuple = ImmutableList.of(b0, b1, ...);

  /**
   * Support removal operations when filtering a filtered multimap. Since a filtered multimap has
   * iterators that don't support remove, passing one to the FilteredEntryMultimap constructor would
   * lead to a multimap whose removal operations would fail. This method combines the predicates to
   * avoid that problem.
   */
  private static <K extends @Nullable Object, V extends @Nullable Object>
      Multimap<K, V> filterFiltered(