docs: private static FileWalkState createFileWalkState(File file) {
  
          File[] contents = file.listFiles();
          List<File> dirs = new ArrayList<File>();
          List<File> files = new ArrayList<File>();
          for (File subFile : contents) {
              if (subFile.isDirectory()) {
                  dirs.add(subFile);
              } else {
                  files.add(subFile);
              }
          }
          return new FileWalkState(file, dirs, files);
      }