docs: @Nullable
    public CloseableReference<V> get(final K key) {
      Preconditions.checkNotNull(key);
      Entry<K, V> oldExclusive;
      CloseableReference<V> clientRef = null;
      synchronized (this) {
        oldExclusive = mExclusiveEntries.remove(key);
        Entry<K, V> entry = mCachedEntries.get(key);
        if (entry != null) {
          clientRef = newClientReference(entry);
        }
      }
      maybeNotifyExclusiveEntryRemoval(oldExclusive);
      maybeUpdateCacheParams();
      maybeEvictEntries();
      return clientRef;
    }