void ensureFileIdIsValid(int fileId) throws IndexOutOfBoundsException {
    if (!records.isValidFileId(fileId)) {
      int maxAllocatedID = records.maxAllocatedID();
      throw new IndexOutOfBoundsException("fileId[" + fileId + "] is outside valid/allocated ids range [1.." + maxAllocatedID + "]");
    }
  }
void ensureFileIdIsValid(int fileId)