if (!(o instanceof CacheKey)) {
                return false;
            }

            CacheKey other = (CacheKey) o;

            return ids.equals(other.ids)
                    && files.equals(other.files)
                    && timestamps.equals(other.timestamps)
                    && sizes.equals(other.sizes);
        }

        @Override
        public String toString() {
            return files.toString();