class ImageDB {

  public ImageSize getImageSize(long imageID) {
    ImageSize result = null;
    lock.readLock().lock();
    try {
      result = sizes.getOrDefault(imageID, null);
    } finally {
      lock.readLock().unlock();
    }
    return result;
  }

  public  ImageDB();
  public  ImageDB(ImageDB copy);

}