code: ReferenceEntry<K, V> getEntry(@Nullable Object key) {
      // does not impact recency ordering
      if (key == null) {
        return null;
      }
      int hash = hash(key);
      return segmentFor(hash).getEntry(key, hash);
    }
docs: Returns the internal entry for the specified key. The entry may be loading, expired, or
  partially collected.