* that tests equivalence using their lengths:
   *
   * {@snippet :
   * equiv.wrap("a").equals(equiv.wrap("b")) // true
   * equiv.wrap("a").equals(equiv.wrap("hello")) // false
   * }
   *
   * <p>Note in particular that an equivalence wrapper is never equal to the object it wraps.
   *
   * {@snippet :
   * equiv.wrap(obj).equals(obj) // always false
   * }
   *
   * @since 10.0

   * fallback}, an exception is thrown, this exception is used as the result of the output {@code
   * Future}.
   *
   * <p>Usage example:
   *
   * {@snippet :
   * ListenableFuture<Integer> fetchCounterFuture = ...;
   *
   * // Falling back to a zero counter in case an exception happens when
   * // processing the RPC to fetch counters.

   *
   * {@snippet :
   * NavigableSet<E> set = synchronizedNavigableSet(new TreeSet<E>());
   *  ...
   * synchronized (set) {
   *   // Must be in the synchronized block
   *   Iterator<E> it = set.iterator();
   *   while (it.hasNext()) {
   *     foo(it.next());
   *   }
   * }
   * }
   *
   * <p>or:
   *
   * {@snippet :

   */
  @Override
  boolean equals(@Nullable Object object);

  /**
   * Returns the hash code for this instance. This is defined as the hash code of
   *
   * {@snippet :
   * Arrays.asList(entriesOnlyOnLeft(), entriesOnlyOnRight(),
   *     entriesInCommon(), entriesDiffering())
   * }
   */
  @Override
  int hashCode();

  /**

 * recursion by calling {@link #visit} for any {@code Type} while visitation is in progress. For
 * example, this can be used to reject wildcards or type variables contained in a type as in:
 *
 * {@snippet :
 * new TypeVisitor() {
 *   protected void visitParameterizedType(ParameterizedType t) {
 *     visit(t.getOwnerType());
 *     visit(t.getActualTypeArguments());
 *   }

 * were inserted, not how those bytes were chunked into discrete put() operations. For example, the
 * following three expressions all generate colliding hash codes:
 *
 * {@snippet :
 * newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
 * newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
 * newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()
 * }
 *

   * java.util.stream} Javadoc), that order is preserved, but entries are <a
   * href="ImmutableMultimap.html#iteration">grouped by key</a>.
   *
   * <p>Example:
   *
   * {@snippet :
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")

     * <p>Returns {@code true} if the given object is also a multiset entry and the two entries
     * represent the same element and count. That is, two entries {@code a} and {@code b} are equal
     * if:
     *
     * {@snippet :
     * Objects.equals(a.getElement(), b.getElement()) && a.getCount() == b.getCount()
     * }
     */
    @Override
    // TODO(kevinb): check this wrt TreeMultiset?
    boolean equals(@Nullable Object o);

   * lists in order; the "n-ary <a href="http://en.wikipedia.org/wiki/Cartesian_product">Cartesian
   * product</a>" of the lists. For example:
   *
   * {@snippet :
   * Lists.cartesianProduct(ImmutableList.of(
   *     ImmutableList.of(1, 2),
   *     ImmutableList.of("A", "B", "C")))
   * }
   *
   * <p>returns a list containing six lists in the following order:
   *

   * java.util.stream} Javadoc), that order is preserved, but entries are <a
   * href="ImmutableMultimap.html#iteration">grouped by key</a>.
   *
   * <p>Example:
   *
   * {@snippet :
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")