class ImmutableKeyValuePairs {

  @Override
  public String toString() {
    final StringBuilder sb = new StringBuilder("{");
    List<Object> data = data();
    for (int i = 0; i < data.size(); i += 2) {
      sb.append(data.get(i)).append("=").append(data.get(i + 1)).append(", ");
    }
    // get rid of that last pesky comma
    if (sb.length() > 1) {
      sb.setLength(sb.length() - 2);
    }
    sb.append("}");
    return sb.toString();
  }

}