code: public static List<String> getAllAncestors(String eventPath) {
      // check if the path is valid.
      if (eventPath == null || !eventPath.startsWith(Path.SEPARATOR)) {
        return null;
      }
      
      if (eventPath.equals(Path.SEPARATOR)) {
        return Arrays.asList(Path.SEPARATOR);
      }
      
      List<String> ancestors = new ArrayList<String>();
      while (eventPath.length() > 0) {
        ancestors.add(eventPath);
        eventPath = eventPath.substring(0, eventPath.lastIndexOf(Path.SEPARATOR));
      }
      // add the root directory
      ancestors.add(Path.SEPARATOR);
      
      return ancestors;
    }
docs: return all the ancestors of the given path, include itself.
  @param eventPath
  @return