code: public void close() throws IOException {
      out.close();
  
      int size = stackSize;
      if (size > 1 || size == 1 && stack[size - 1] != NONEMPTY_DOCUMENT) {
        throw new IOException("Incomplete document");
      }
      stackSize = 0;
    }
docs: Flushes and closes this writer and the underlying {@link Writer}.
  
  @throws IOException if the JSON document is incomplete.