code: public DRUMSReader<Data> getReader() throws FileLockException, IOException {
          if (reader_instance != null && !reader_instance.filesAreOpened) {
              reader_instance.openFiles();
          } else {
              reader_instance = new DRUMSReader<Data>(this);
          }
          return reader_instance;
      }
docs: Returns a {@link DRUMSReader}. If the {@link DRUMSReader} was not instantiated yet, it will be instantiated. If
  there exists an instance, but the files were already closed, the files will be reopened.<br>
  <br>
  Remember, if you have an opened Reader. You can't synchronize buckets.
  
  @return a pointer to the internal {@link DRUMSReader}-instance
  @throws IOException
  @throws FileLockException