code: @Override
    public boolean undelete(Path f, String userName) throws IOException {
      List<Codec> codecList = Codec.getCodecs();
      Path[] parityPathList = new Path[codecList.size()];
  
      for (int i=0; i<parityPathList.length; i++) {
        parityPathList[i] = new Path(codecList.get(i).parityDirectory, 
                                     makeRelative(f));
      }
  
      // undelete the src file.
      if (!fs.undelete(f, userName)) {
        return false;
      }
  
      // try to undelete the parity file
      for (Path parityPath : parityPathList) {
        fs.undelete(parityPath, userName);
      }
      return true;
    }
docs: undelete the parity file together with the src file.