code: public OpenFileInfo[] iterativeGetOpenFiles(Path prefix, int millis, String start)
      throws IOException {
      throw new UnsupportedOperationException(
        getClass().getCanonicalName() + " does not support iterativeGetOpenFiles");
    }
docs: Fetch the list of files that have been open longer than a
  specified amount of time.
  @param prefix path prefix specifying subset of files to examine
  @param millis select files that have been open longer that this
  @param start where to start searching in the case of subsequent calls, or null
  @return array of OpenFileInfo objects
  @throw IOException