code: public UrlStringBuilder addParameter(String name, String... values) {
          this.addParameter(name, values != null ? Arrays.asList(values) : null);
          return this;
      }
docs: Adds to a URL parameter, if a parameter with the same name already exists its values are
  added to
  
  @param name Parameter name, can not be null
  @param values Values for the parameter, null is valid
  @return this