*
   * <p><b>{@code Stream} equivalent:</b> {@code stream.filter(type::isInstance).map(type::cast)}.
   * This does perform a little more work than necessary, so another option is to insert an
   * unchecked cast at some later point:
   *
   * <pre>
   * {@code @SuppressWarnings("unchecked") // safe because of ::isInstance check
   * ImmutableList<NewType> result =

      // even though K doesn't explicitly implement Comparable.
      comparator = (Comparator<? super K>) NATURAL_ORDER;
    }
    if (map instanceof ImmutableSortedMap) {
      // TODO(kevinb): Prove that this cast is safe, even though
      // Collections.unmodifiableSortedMap requires the same key type.
      @SuppressWarnings("unchecked")
      ImmutableSortedMap<K, V> kvMap = (ImmutableSortedMap<K, V>) map;

      Multiset<? extends E> multiset) {
    if (multiset instanceof UnmodifiableMultiset || multiset instanceof ImmutableMultiset) {
      @SuppressWarnings("unchecked") // Since it's unmodifiable, the covariant cast is safe
      Multiset<E> result = (Multiset<E>) multiset;
      return result;
    }
    return new UnmodifiableMultiset<>(checkNotNull(multiset));
  }

  /**
   * Simply returns its argument.
   *

   * the provided key, an empty immutable set is returned. The values are in the same order as the
   * parameters used to build this multimap.
   */
  @Override
  public ImmutableSet<V> get(K key) {
    // This cast is safe as its type is known in constructor.
    ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
    return MoreObjects.firstNonNull(set, emptySet);
  }

  public E higher(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, false), null);
  }

  @Override
  public E first() {
    return iterator().next();
  }

  @Override
  public E last() {
    return descendingIterator().next();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always

   * the discussion in the {@link ListenableFuture#addListener ListenableFuture.addListener}
   * documentation.
   */
  public void add(Runnable runnable, Executor executor) {
    // Fail fast on a null. We throw NPE here because the contract of Executor states that it throws
    // NPE on null listener, so we propagate that contract up into the add method as well.
    checkNotNull(runnable, "Runnable was null.");

        // the listener is responsible for calling completeWithFuture, directExecutor is appropriate
        // since all we are doing is unpacking a completed future which should be fast.
        try {
          future.addListener(valueToSet, DirectExecutor.INSTANCE);
        } catch (Throwable t) {
          // Any Exception is either a RuntimeException or sneaky checked exception.
          //

      }
    }

    /**
     * Associates {@code key} with {@code value} in the built map. If the same key is put more than
     * once, {@link #buildOrThrow} will fail, while {@link #buildKeepingLast} will keep the last
     * value put for that key.
     */
    @CanIgnoreReturnValue
    public Builder<K, V> put(K key, V value) {
      ensureCapacity(size + 1);
      checkEntryNotNull(key, value);

      return Iterators.find(unfiltered.iterator(), predicate);
    }

    @Override
    @ParametricNullness
    public E last() {
      SortedSet<E> sortedUnfiltered = (SortedSet<E>) unfiltered;
      while (true) {
        E element = sortedUnfiltered.last();
        if (predicate.apply(element)) {
          return element;
        }
        sortedUnfiltered = sortedUnfiltered.headSet(element);

2.  APIs without `@Beta` will remain binary-compatible for the indefinite
    future. (Previously, we sometimes removed such APIs after a deprecation
    period. The last release to remove non-`@Beta` APIs was Guava 21.0.) Even
    `@Deprecated` APIs will remain (again, unless they are `@Beta`). We have no
    plans to start removing things again, but officially, we're leaving our