cache.asMap().put(extraKey, extraKey);
    assertThat(cache.asMap().get(extraKey)).isSameInstanceAs(extraKey);

    Object[] lookupKeys = new Object[] {new Object(), new Object(), new Object()};
    assertThrows(InvalidCacheLoadException.class, () -> cache.getAll(asList(lookupKeys)));

    for (Object key : lookupKeys) {
      assertThat(cache.asMap().containsKey(key)).isTrue();
    }

    Map<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);
    assertEquals(ImmutableMap.of("one", 3, "two", 3, "three", 5), map);
    assertEquals(Integer.valueOf(3), map.remove("two"));
    assertThat(strings).containsExactly("one", "three").inOrder();
  }

  public void testAsMapEmpty() {
    Set<String> strings = ImmutableSet.of();
    Map<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);

    cache.asMap().put(extraKey, extraKey);
    assertThat(cache.asMap().get(extraKey)).isSameInstanceAs(extraKey);

    Object[] lookupKeys = new Object[] {new Object(), new Object(), new Object()};
    assertThrows(InvalidCacheLoadException.class, () -> cache.getAll(asList(lookupKeys)));

    for (Object key : lookupKeys) {
      assertThat(cache.asMap().containsKey(key)).isTrue();
    }

   * access. Access time is reset by all cache read and write operations (including {@code
   * Cache.asMap().get(Object)} and {@code Cache.asMap().put(K, V)}), but not by {@code
   * containsKey(Object)}, nor by operations on the collection-views of {@link Cache#asMap}}. So,
   * for example, iterating through {@code Cache.asMap().entrySet()} does not reset access time for
   * the entries you retrieve.
   *

  }

  /**
   * Returns {@link SetMultimap#asMap multimap.asMap()}, with its type corrected from {@code Map<K,
   * Collection<V>>} to {@code Map<K, Set<V>>}.
   *
   * @since 15.0
   */
  @SuppressWarnings("unchecked")
  // safe by specification of SetMultimap.asMap()
  public static <K extends @Nullable Object, V extends @Nullable Object> Map<K, Set<V>> asMap(

    Map<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);
    assertEquals(ImmutableMap.of("one", 3, "two", 3, "three", 5), map);
    assertEquals(Integer.valueOf(3), map.remove("two"));
    assertThat(strings).containsExactly("one", "three").inOrder();
  }

  public void testAsMapEmpty() {
    Set<String> strings = ImmutableSet.of();
    Map<String, Integer> map = Maps.asMap(strings, LENGTH_FUNCTION);

   * access. Access time is reset by all cache read and write operations (including {@code
   * Cache.asMap().get(Object)} and {@code Cache.asMap().put(K, V)}), but not by {@code
   * containsKey(Object)}, nor by operations on the collection-views of {@link Cache#asMap}}. So,
   * for example, iterating through {@code Cache.asMap().entrySet()} does not reset access time for
   * the entries you retrieve.
   *

        }
        return entries;
      }
    }

    @Override
    public Map<K, Collection<V>> asMap() {
      synchronized (mutex) {
        if (asMap == null) {
          asMap = new SynchronizedAsMap<>(delegate().asMap(), mutex);
        }
        return asMap;
      }
    }

    @Override
    public Multiset<K> keys() {
      synchronized (mutex) {

        delegate().forEach(action);
      }
    }

    @Override
    public Map<K, Collection<V>> asMap() {
      synchronized (mutex) {
        if (asMap == null) {
          asMap = new SynchronizedAsMap<>(delegate().asMap(), mutex);
        }
        return asMap;
      }
    }

    @Override
    public Multiset<K> keys() {
      synchronized (mutex) {