code: private void addQueryStringPair(String cleanKey, Object rawValue, StringBuilder queryStringBuilder)
      {
          // Serialize null values as an empty string.
          String valueAsString = rawValue == null ? "" : String.valueOf(rawValue);
          String cleanValue = this.url(valueAsString);
          if (queryStringBuilder.length() != 0) {
              queryStringBuilder.append(AND);
          }
          queryStringBuilder.append(cleanKey).append(EQUALS).append(cleanValue);
      }
docs: Method to add an key / value pair to a query String.
  
  @param cleanKey Already escaped key
  @param rawValue Raw value associated to the key
  @param queryStringBuilder String Builder containing the current query string