code: protected void initCheck() throws IOException {
      // Check storage version
      if (_version != STORAGE_VERSION) {
        throw new IOException("Invalid version in " + _file.getName() + ": "
                + _version + ", " + STORAGE_VERSION + " expected");
      }
      
      // Check array file header
      if(!checkHeader()) {
        throw new IOException("Invalid header in " + _file.getName() + ": " + getHeader());
      }
    }
docs: Checks the header of this ArrayFile upon initial loading.
  
  @throws IOException the header is not valid.