使用lamb遍历多个嵌套列表

Question

如何在已经使用lambda遍历另一个列表的同时遍历一个列表？我有1个汽车对象，是我正在遍历的Something对象的列表，在执行此操作时，我需要遍历每个Wheel对象。输出是不同对象Clean的列表。

    Car car = new Car();
    List<Something> somethings = new ArrayList<Something>();
    //say we have multiple items in this List
    List<Clean> cleanList =
             somethings.stream()
                    .map(something -> {
                        return car.wheels.stream().map(wheel -> something.clean(car, wheel));                        })
                    .collect(Collectors.toList());

对于以下对象，

class Car {

    String carId;

    String carName;

    List<Wheel> wheels;
}

class Wheel {

    String wheelId;

    String wheelType;
}

class Something {

    String somethingId;

    String somethingType;

    public Clean clean(Car car, Wheel wheel) {
        return new Clean();
    }
}

class Clean {

    String cleanId;

    String cleanType;
}

我想遍历汽车所有车轮的所有物件。我尝试过这样做，但是没有用。

Answer 1

您需要将其展平，所以flatMap可以做到

List<Clean> cleanList =
            somethings.stream()
                    .flatMap(something -> car.wheels.stream().map(wheel -> something.clean(car, wheel)))
                    .collect(Collectors.toList());