code: public boolean accept(File file) {
      if (file.isDirectory()) {
        return recursively;
      } else {
        String filename = file.getName();
        return accept(filename);
      }
    }
docs: Checks whether a file satisfies the number range selection filter.
  The test is evaluated based on the rightmost natural number found in
  the filename string (proper, not including directories in a path).
  
  @param file The file
  @return true If the file is within the ranges filtered for