code: public static String encodeForms(Collection<? extends Parameter<String>> queries, Charset charset) {
          StringBuilder sb = new StringBuilder();
          try {
              for (Parameter<String> query : queries) {
                  sb.append(URLEncoder.encode(query.name(), charset.name()));
                  sb.append('=');
                  sb.append(URLEncoder.encode(query.value(), charset.name()));
                  sb.append('&');
              }
          } catch (UnsupportedEncodingException e) {
              // should not happen
              throw new RequestsException(e);
          }
          if (sb.length() > 0) {
              sb.deleteCharAt(sb.length() - 1);
          }
          return sb.toString();
      }
docs: Encode multi form parameters