code: protected String toParameterString(boolean withJsonParameter, Parameter... parameters) {
      if (!isBlank(accessToken)) {
        parameters = parametersWithAdditionalParameter(Parameter.with(ACCESS_TOKEN_PARAM_NAME, accessToken), parameters);
      }
  
      if (!isBlank(accessToken) && !isBlank(appSecret)) {
        parameters = parametersWithAdditionalParameter(
          Parameter.with(APP_SECRET_PROOF_PARAM_NAME, obtainAppSecretProof(accessToken, appSecret)), parameters);
      }
  
      if (withJsonParameter) {
        parameters = parametersWithAdditionalParameter(Parameter.with(FORMAT_PARAM_NAME, "json"), parameters);
      }
  
      StringBuilder parameterStringBuilder = new StringBuilder();
      boolean first = true;
  
      for (Parameter parameter : parameters) {
        if (first) {
          first = false;
        } else {
          parameterStringBuilder.append("&");
        }
  
        parameterStringBuilder.append(urlEncode(parameter.name));
        parameterStringBuilder.append("=");
        parameterStringBuilder.append(urlEncodedValueForParameterName(parameter.name, parameter.value));
      }
  
      return parameterStringBuilder.toString();
    }
docs: Generate the parameter string to be included in the Facebook API request.
  
  @param withJsonParameter
  add additional parameter format with type json
  @param parameters
  Arbitrary number of extra parameters to include in the request.
  @return The parameter string to include in the Facebook API request.
  @throws FacebookJsonMappingException
  If an error occurs when building the parameter string.