code: public <T extends RequestParameter> void addParameters(final List<T> params)
     {
        for (RequestParameter rp : params)
        {
           String value = rp.getValue();
           String name = rp.getName();
  
           if (!parameters.containsKey(name))
           {
              ArrayList<String> values = new ArrayList<String>();
              if (value != null)
              {
                 values.add(value);
              }
              parameters.put(name, values);
           }
           else
           {
              parameters.get(name).add(value);
           }
        }
     }
docs: Add query parameters from the given list of {@link RequestParameter} objects. If a parameter already exists,
  append new values to the existing list of values for that parameter.