/* Map can be empty if it's an EnumHashBiMap. */
    Map<Currency, String> emptyBimap = EnumHashBiMap.create(Currency.class);
    bimap = EnumHashBiMap.create(emptyBimap);
    assertTrue(bimap.isEmpty());

    /* Map can be empty if it's an EnumBiMap. */
    Map<Currency, Country> emptyBimap2 = EnumBiMap.create(Currency.class, Country.class);
    EnumHashBiMap<Currency, Country> bimap2 = EnumHashBiMap.create(emptyBimap2);

    if (map instanceof EnumBiMap) {
      return ((EnumBiMap<K, ?>) map).keyTypeOrObjectUnderJ2cl;
    }
    if (map instanceof EnumHashBiMap) {
      return ((EnumHashBiMap<K, ?>) map).keyTypeOrObjectUnderJ2cl;
    }
    checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.keySet().iterator().next());
  }

    if (map instanceof EnumBiMap) {
      return ((EnumBiMap<K, ?>) map).keyTypeOrObjectUnderJ2cl;
    }
    if (map instanceof EnumHashBiMap) {
      return ((EnumHashBiMap<K, ?>) map).keyTypeOrObjectUnderJ2cl;
    }
    checkArgument(!map.isEmpty());
    return getDeclaringClassOrObjectForJ2cl(map.keySet().iterator().next());
  }

 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableBiMap}
 *   <li>{@link HashBiMap}
 *   <li>{@link EnumBiMap}
 *   <li>{@link EnumHashBiMap}
 * </ul>
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */

 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableBiMap}
 *   <li>{@link HashBiMap}
 *   <li>{@link EnumBiMap}
 *   <li>{@link EnumHashBiMap}
 * </ul>
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */

        IllegalArgumentException.class,
        () -> EnumBiMap.create(Collections.<Currency, Country>emptyMap()));
    assertThrows(
        IllegalArgumentException.class,
        () -> EnumBiMap.create(EnumHashBiMap.<Currency, Country>create(Currency.class)));

    /* Map can be empty if it's an EnumBiMap. */
    Map<Currency, Country> emptyBimap = EnumBiMap.create(Currency.class, Country.class);