* in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:
 *
 * {@snippet :
 * ConcurrentMap<Request, Stopwatch> timers = new MapMaker()
 *     .concurrencyLevel(4)
 *     .weakKeys()
 *     .makeMap();
 * }
 *
 * <p>These features are all optional; {@code new MapMaker().makeMap()} returns a valid concurrent
 * map that behaves similarly to a {@link ConcurrentHashMap}.
 *

 * maximumSize}, {@link #maximumWeight(long) maximumWeight}, {@link #expireAfterWrite
 * expireAfterWrite}, {@link #expireAfterAccess expireAfterAccess}, {@link #weakKeys weakKeys},
 * {@link #weakValues weakValues}, or {@link #softValues softValues} are requested.
 *
 * <p>If {@link #maximumSize(long) maximumSize} or {@link #maximumWeight(long) maximumWeight} is

            } else {
              return "0";
            }
          }
        };

    LoadingCache<Integer, String> recursiveCache =
        CacheBuilder.newBuilder().weakKeys().weakValues().build(recursiveLoader);
    cacheRef.set(recursiveCache);
    assertEquals("3, 2, 1, 0", recursiveCache.getUnchecked(3));

    recursiveLoader =
        new CacheLoader<Integer, String>() {

  /** Returns an iterable containing all combinations weakKeys and weak/softValues. */
  private static Iterable<CacheBuilder<Object, Object>> allKeyValueStrengthMakers() {
    return ImmutableList.of(
        createCacheBuilder(),
        createCacheBuilder().weakValues(),
        createCacheBuilder().softValues(),
        createCacheBuilder().weakKeys(),
        createCacheBuilder().weakKeys().weakValues(),

   * created and objects of the same class are registered on all of them.
   */
  private static final LoadingCache<Class<?>, ImmutableList<Method>> subscriberMethodsCache =
      CacheBuilder.newBuilder()
          .weakKeys()
          .build(CacheLoader.from(SubscriberRegistry::getAnnotatedMethodsNotCached));

  /**
   * Returns all subscribers for the given listener grouped by the type of event they subscribe to.
   */

        ConcurrentMap<K, V> newMap = new MapMaker().weakKeys().makeMap();
        checkState(newMap instanceof MapMakerInternalMap);
        newMap.putAll(map);
        return newMap;
      }
    },
    MapMakerWeakKeysWeakValues {
      @Override
      public <K extends Comparable<K>, V> Map<K, V> create(Map<K, V> map) {
        ConcurrentMap<K, V> newMap = new MapMaker().weakKeys().weakValues().makeMap();

        () -> CacheBuilder.newBuilder().maximumSize(1).weigher(constantWeigher(42)));
  }

  @GwtIncompatible // weakKeys
  public void testKeyStrengthSetTwice() {
    CacheBuilder<Object, Object> builder1 = CacheBuilder.newBuilder().weakKeys();
    assertThrows(IllegalStateException.class, () -> builder1.weakKeys());
  }

  @GwtIncompatible // weakValues
  public void testValueStrengthSetTwice() {

        () -> CacheBuilder.newBuilder().maximumSize(1).weigher(constantWeigher(42)));
  }

  @GwtIncompatible // weakKeys
  public void testKeyStrengthSetTwice() {
    CacheBuilder<Object, Object> builder1 = CacheBuilder.newBuilder().weakKeys();
    assertThrows(IllegalStateException.class, () -> builder1.weakKeys());
  }

  @GwtIncompatible // weakValues
  public void testValueStrengthSetTwice() {

   * that reclamation becomes important.
   */
  @J2ktIncompatible
  static MapMaker tryWeakKeys(MapMaker mapMaker) {
    return mapMaker.weakKeys();
  }

  static <E extends Enum<E>> Class<E> getDeclaringClassOrObjectForJ2cl(E e) {
    return e.getDeclaringClass();
  }

  static int reduceIterationsIfGwt(int iterations) {
    return iterations;

   * that reclamation becomes important.
   */
  @J2ktIncompatible
  static MapMaker tryWeakKeys(MapMaker mapMaker) {
    return mapMaker.weakKeys();
  }

  static <E extends Enum<E>> Class<E> getDeclaringClassOrObjectForJ2cl(E e) {
    return e.getDeclaringClass();
  }

  static int reduceIterationsIfGwt(int iterations) {
    return iterations;