return new ConstantLoader<>(constant);
  }

  /** Returns a {@link CacheLoader} that returns the given {@code constant} for every request. */
  static IncrementingLoader incrementingLoader() {
    return new IncrementingLoader();
  }

  /** Returns a {@link CacheLoader} that throws the given error for every request. */
  static <K, V> CacheLoader<K, V> errorLoader(final Error e) {
    checkNotNull(e);