Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

      Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

        NullPointerException.class, () -> multimap().putAll(k3(), newArrayList(v3(), null)));

    Collection<V> values = multimap().get(k3());
    if (values.size() == 0) {
      expectUnchanged();
      // Be extra thorough in case internal state was corrupted by the expected null.
      assertEquals(new ArrayList<>(), new ArrayList<>(values));
      assertEquals(size, multimap().size());
    } else {

    if (multimap.isEmpty() && valueComparator == null) {
      return of();
    }

    if (multimap instanceof ImmutableSetMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }
    }

      ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }
    }

    return fromMapEntries(multimap.asMap().entrySet(), null);
  }

  /**
   * Returns an immutable multimap containing the specified entries. The returned multimap iterates

    if (multimap.isEmpty() && valueComparator == null) {
      return of();
    }

    if (multimap instanceof ImmutableSetMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }
    }

      ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }
    }

    return fromMapEntries(multimap.asMap().entrySet(), null);
  }

  /**
   * Returns an immutable multimap containing the specified entries. The returned multimap iterates

   * {@code multimap}.
   */
  public <K extends K0, V extends V0> Multimap<K, V> build(
      Multimap<? extends K, ? extends V> multimap) {
    Multimap<K, V> result = build();
    result.putAll(multimap);
    return result;
  }

  /**
   * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
   *
   * @since 16.0
   */
  public abstract static class ListMultimapBuilder<

   * {@code multimap}.
   */
  public <K extends K0, V extends V0> Multimap<K, V> build(
      Multimap<? extends K, ? extends V> multimap) {
    Multimap<K, V> result = build();
    result.putAll(multimap);
    return result;
  }

  /**
   * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
   *
   * @since 16.0
   */
  public abstract static class ListMultimapBuilder<

    } catch (UnsupportedOperationException expected) {
    }
    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #putAll(Multimap<K, V>)
    Multimap<K, V> multimap2 = ArrayListMultimap.create();
    multimap2.put(sampleKey, sampleValue);
    try {
      multimap.putAll(multimap2);
      fail("putAll(Multimap<K, V>) succeeded on unmodifiable multimap");