}

  /**
   * Specifies a nanosecond-precision time source for this cache. By default, {@link
   * System#nanoTime} is used.
   *
   * <p>The primary intent of this method is to facilitate testing of caches with a fake or mock
   * time source.
   *
   * @return this {@code CacheBuilder} instance (for chaining)
   * @throws IllegalStateException if a ticker was already set