code: private void validateAll() throws OptionValidationException {
          boolean unattended = getBooleanValue(UNATTENDED, false);
          for (String optionId : getOptionNames()) {
              OptionDefinition opt = OptionDefinition.get(optionId, this);
              if (opt == null) {
                  throw new OptionValidationException("Option is not defined", optionId);
              }
              opt.validateValue(getValue(optionId), unattended);
          }
      }
docs: Validate the options, assuming defaults have already been applied.
  Validation for a given option might entail more than a syntax check. It
  might check whether a given directory exists, for example.