code: private void listStatus(ArrayList<FileStatus> results, Path f,
        PathFilter filter) throws IOException {
      FileStatus listing[] = listStatus(f);
      if (listing == null) {
        throw new FileNotFoundException("File " + f + " does not exist");
      }
      for (int i = 0; i < listing.length; i++) {
        if (filter.accept(listing[i].getPath())) {
          results.add(listing[i]);
        }
      }
    }
docs: /*
  Filter files/directories in the given path using the user-supplied path
  filter. Results are added to the given array <code>results</code>.