Map

inputString.map(x -> {
    if (!StringUtils.isBlank(x)) {
        return x;
    } else {
        return Optional.empty();
    }
}).orElse(Optional.empty());

Filter

Java < 16

return thing.getAllSubEntities()
        .stream()
        .filter(e -> e.isDisabled())
        .collect(Collectors.toList());

Java >= 16

return thing.getAllSubEntities()
        .stream()
        .filter(e -> e.isDisabled())
        .tolist();