Java <Streams> How to sort a list of my objects based on counting list components

Question

I have 2 classes in Java. One of them is the Car class, which consists of 5 variables. Among them, I have a List List variable. Another class contains a list of objects of the Car class: List carlist.

My task: I need to sort the list of car objects using Streams in Java, based on the number of pieces of equipment that this car has.

How should I do it? I tried to create a separate method for counting the elements in the list of the object, but then inside the Comparator I can not put the object as an argument to this method.

Here is an excerpt of my code:

private int countEquipmentItems (Car s){
    if (s == null){
        return 0;
    }
    int countEquipment = 0;
    List<String> a = s.getEquipment();
    for (int i = 0; i <a.size() ; i++) {
        countEquipment ++;
    }
    return countEquipment;
}

And I tried using this method in a thread:

public void sortbyEquipment (List<Car> carList){
    carList.stream()
            .sorted(Comparator.comparing(countEquipmentItems(Car s)));
    }
}

I appreciate any help

Answer 1

countEquipmentItems . car.getEquipment().size():

public void sortbyEquipment (List<Car> carList){
    carList.stream()
           .sorted(Comparator.comparing(car -> car.getEquipment().size()))
           ...
}

, Comparator Collections.sort(), Stream.

Answer 2

countEquipmentItems .

, , sort , List<T>.

carList.sort(Comparator.comparingInt(car -> car.getEquipment().size()));

, , :

List<Car> clonedList = new ArrayList<>(carList); // clone the carList
clonedList.sort(Comparator.comparingInt(car -> car.getEquipment().size()));