A use-case I've had for a quick right-biased Java Either I threw together is handling a migration from java.util.Date to java.time.LocalDate:

    List<LocalDate> dobs = users.stream()
        .map(person -> Either.either(person::getDeprecatedDob, person::getDobLocalDate))
        .map(oldOrNewFormat -> oldOrNewFormat.fold(
            (Date oldFormat) -> convertOldFormatToNew(oldFormat),
            (LocalDate newFormat) -> newFormat,
         ))
        .collect(Collectors.toList());

I use the right-biased-ness of the Either to prefer the new format, if available, but failing that, use the old format and then convert as needed.