@Override
  public String toString() {
    StringBuilder s = new StringBuilder("{");
    for (int i = 0; i < keys.length; i++) {
      int key = keys[i];
      Object value = values[i];
      s.append(s.length() == 1 ? "" : ", ").append(Key.getKeyByIndex(key)).append("=").append(value);
    }
    return s.append("}").toString();
  }
@Override
  public String toString()