/**
   * Returns a descending view of this multiset. Modifications made to either map will be reflected
   * in the other.
   */
  SortedMultiset<E> descendingMultiset();

  /**
   * Returns a view of this multiset restricted to the elements less than {@code upperBound},
   * optionally including {@code upperBound} itself. The returned multiset is a view of this

 * ...
 * }</pre>
 *
 * <h3>Views</h3>
 *
 * <p>Much of the power of the multimap API comes from the <i>view collections</i> it provides.
 * These always reflect the latest state of the multimap itself. When they support modification, the
 * changes are <i>write-through</i> (they automatically update the backing multimap). These view
 * collections are:
 *
 * <ul>
 *   <li>{@link #asMap}, mentioned above

   *
   * @param multiset the multiset for which an unmodifiable view is to be generated
   * @return an unmodifiable view of the multiset
   */
  public static <E extends @Nullable Object> Multiset<E> unmodifiableMultiset(
      Multiset<? extends E> multiset) {
    if (multiset instanceof UnmodifiableMultiset || multiset instanceof ImmutableMultiset) {

 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Ints} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.
 *   <li>Access to all collection-based utilities via {@link #asList} (though at the cost of
 *       allocating garbage).

            iterator.remove();
          }
        };
      }
    };
  }

  /**
   * Returns a view of {@code iterable} containing its first {@code limitSize} elements. If {@code
   * iterable} contains fewer than {@code limitSize} elements, the returned view contains all of its
   * elements. The returned iterable's iterator supports {@code remove()} if {@code iterable}'s
   * iterator does.
   *

 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Doubles} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.
 *   <li>Access to all collection-based utilities via {@link #asList} (though at the cost of
 *       allocating garbage).

    modCount++;
  }

  /** Shared supertype of keySet, values, entrySet, and inverse.entrySet. */
  abstract static class View<
          K extends @Nullable Object, V extends @Nullable Object, T extends @Nullable Object>
      extends AbstractSet<T> {
    final HashBiMap<K, V> biMap;

    View(HashBiMap<K, V> biMap) {
      this.biMap = biMap;
    }

    @ParametricNullness
    abstract T forEntry(int entry);

  Entry<E> firstEntry();

  @CheckForNull
  Entry<E> lastEntry();

  @CheckForNull
  Entry<E> pollFirstEntry();

  @CheckForNull
  Entry<E> pollLastEntry();

  /**
   * Returns a {@link SortedSet} view of the distinct elements in this multiset. (Outside GWT, this
   * returns a {@code NavigableSet}.)
   */
  @Override
  SortedSet<E> elementSet();

  SortedMultiset<E> descendingMultiset();

    return Lists.newArrayList(0);
  }

  /**
   * The version of this test supplied by {@link MapInterfaceTest} fails for this particular Map
   * implementation, because {@code map.get()} returns a view collection that changes in the course
   * of a call to {@code remove()}. Thus, the expectation doesn't hold that {@code map.remove(x)}
   * returns the same value which {@code map.get(x)} did immediately beforehand.
   */

@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Collections2 {
  private Collections2() {}

  /**
   * Returns the elements of {@code unfiltered} that satisfy a predicate. The returned collection is
   * a live view of {@code unfiltered}; changes to one affect the other.
   *
   * <p>The resulting collection's iterator does not support {@code remove()}, but all other