* Undefined behavior and bugs will result.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
 *
 * @author Mike Ward
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public class ImmutableSetMultimap<K, V> extends ImmutableMultimap<K, V>
    implements SetMultimap<K, V> {
  /**

   * A builder for creating immutable sorted map instances, especially {@code public static final}
   * maps ("constant maps"). Example:
   *
   * <pre>{@code
   * static final ImmutableSortedMap<Integer, String> INT_TO_WORD =
   *     new ImmutableSortedMap.Builder<Integer, String>(Ordering.natural())
   *         .put(1, "one")
   *         .put(2, "two")
   *         .put(3, "three")
   *         .buildOrThrow();
   * }</pre>

  }

  /**
   * A builder for creating immutable map instances, especially {@code public static final} maps
   * ("constant maps"). Example:
   *
   * <pre>{@code
   * static final ImmutableMap<String, Integer> WORD_TO_INT =
   *     new ImmutableMap.Builder<String, Integer>()
   *         .put("one", 1)
   *         .put("two", 2)
   *         .put("three", 3)
   *         .buildOrThrow();
   * }</pre>
   *

  /**
   * A builder for creating immutable bimap instances, especially {@code public static final} bimaps
   * ("constant bimaps"). Example:
   *
   * <pre>{@code
   * static final ImmutableBiMap<String, Integer> WORD_TO_INT =
   *     new ImmutableBiMap.Builder<String, Integer>()
   *         .put("one", 1)
   *         .put("two", 2)
   *         .put("three", 3)
   *         .buildOrThrow();
   * }</pre>
   *

    @Override
    public int hashCode() {
      // Warning: this is broken if size() == 0, so it is critical that we
      // substitute an empty ImmutableSet to the user in place of this

      // It's a weird formula, but tests prove it works.
      int adjust = size() - 1;
      for (int i = 0; i < axes.size(); i++) {
        adjust *= 31;
        adjust = ~~adjust;

          return null;
        }
      }
      return topMetaIterator;
    }

    @Override
    public boolean hasNext() {
      while (!checkNotNull(iterator).hasNext()) {
        // this weird checkNotNull positioning appears required by our tests, which expect
        // both hasNext and next to throw NPE if an input iterator is null.

        topMetaIterator = getTopMetaIterator();