code: public void addParameters(final Map<String, String[]> params)
     {
        if (params != null)
        {
           for (Entry<String, String[]> entry : params.entrySet())
           {
              List<String> values = null;
              if (entry.getValue() != null)
              {
                 values = Arrays.asList(entry.getValue());
              }
              parameters.put(entry.getKey(), values);
           }
        }
     }
docs: Add parameters from the given map of name=value pairs. For parameters with more than one value, each value will be
  appended using the same name. If a parameter already exists, append new values to the existing list of values for
  that parameter.