code: @Override
      public boolean isDateAllowed(LocalDate date) {
          if ((firstAllowedDate != null) && (date.isBefore(firstAllowedDate))) {
              return false;
          }
          if ((lastAllowedDate != null) && (date.isAfter(lastAllowedDate))) {
              return false;
          }
          return true;
      }
docs: isDateAllowed, This implements the DateVetoPolicy interface. This returns true if the date is
  allowed, otherwise this returns false. The value of null will never be passed to this
  function, under any case.