code: public InputStream getInput(String pathname) throws FileNotFoundException {
        GridFile file = (GridFile) getFile(pathname);
        checkFileIsReadable(file);
        return new GridInputStream(file, data);
     }
docs: Opens an InputStream for reading from the file denoted by pathname.
  @param pathname the full path of the file to read from
  @return an InputStream for reading from the file
  @throws FileNotFoundException if the file does not exist or is a directory