How, using a Stream, to add the elements of a List to another sheet, while returning the added elements?

Question

Iron

There is a list of cars
List<Car> cars = new ArrayList<>();
as well as the addCars method, which takes a list of cars and whose essence is to add only BMW cars to the collection, after which the method returns all the added cars, and if no cars have been added, then an empty Optional. You need to implement this using Stream.API

Stuck at this point:

public Optional<Car> addCars(List<Car> inputCars) {

        inputCars.stream()
                .filter(car -> car.getMark().equals(Mark.BMW)
    }

Answer 1

operatives immediately 16
Prots Risen 7 1700x norms, I have one in boost 3.9 max temperature games + stream up to 65 degrees, cooling is not dropsy.
1070 you can take it, I did it :), and it's still under warranty for a year and a half.

Answer 2

public Optional<List<Car>> addCars(List<Car> inputCars) {
    retrurn Optional.of(inputCars.stream()
            .filter(Objects::nonNull)
            .filter(car -> Mark.BMW.equals(car.getMark()))
            .collect(Collectors.toList()))
        .filter(cars -> !cars.isEmpty());
}