code: public String normalizeRequestParameters() throws IOException {
          if (requestParameters == null) {
              return "";
          }
  
          StringBuilder sb = new StringBuilder();
          Iterator<String> iter = requestParameters.keySet().iterator();
  
          for (int i = 0; iter.hasNext(); i++) {
              String param = iter.next();
  
              if (OAuth.OAUTH_SIGNATURE.equals(param) || "realm".equals(param)) {
                  continue;
              }
  
              if (i > 0) {
                  sb.append("&");
              }
  
              sb.append(requestParameters.getAsQueryString(param));
          }
          return sb.toString();
      }
docs: Normalizes the set of request parameters this instance was configured
  with, as per OAuth spec section 9.1.1.
  
  @param parameters
  the set of request parameters
  @return the normalized params string
  @throws IOException