code: String remainder() {
          List<String> rem = new ArrayList<>();
          while (next() != null) {
              rem.add(sval);
          }
          return String.join(" ", rem);
      }
docs: Consume the remainder of the input. This is useful to sure all options
  have been encountered and to check to unexpected additional non-option
  input.
  
  @return the string-separated concatenation of all remaining non-option
  arguments.