Java iterate a list and add to object containing a list

Question

I have few object say: Car, Auto and AutoCar

Car
- String name;
- String origin;

Auto
- String type;

AutoCar
-   String type;
-   List<Car> cars = new ArrayList<Car>();

Iterating for list of autos:

List<Car> carList = //fetched from a service or method
List<AutoCar> acList = new ArrayList<AutoCar>();

for(Auto auto : autos){
    AutoCar ac = new AutoCar();
    ac.setType(auto.getType());
    ac.setCars(carList);
    acList.add(ac);
}

I would expect result:

Type = CAR-Type-1
Cars:
name: FORD
origin: US
name: Suzuki
origin: Japan

Type = CAR-Type-2
Cars:
name: Volkswagen
origin: Germany
name: Audi
origin: Germany

Type = CAR-Type-3
Cars:
name: Jaguar
origin: UK
name: Ferrari
origin: Italy

But what I get is the last iteration preserved...

Cars:
name: Jaguar
origin: UK
name: Ferrari
origin: Italy

for all car Types (CAR-Type-1/CAR-Type-2/CAR-Type-3)

I think I am doing it wrong at this line:

ac.setCars(carList);

Please let me know if I am not clear.

I don't think there is enough info here. Is carList correctly filled before you enter this loop? Are you updating it anywhere else? Can you check the value before it enters the loop? — But I'm Not A Wrapper Class
– But I'm Not A Wrapper Class, Commented Apr 24, 2015 at 12:45
do you want to get all cars of same type? or do I get you wrong? — sodik
– sodik, Commented Apr 24, 2015 at 12:46
You should get a new carList in each iteration of your loop; otherwise, you are setting the same list in all AutoCars — yvilbe
– yvilbe, Commented Apr 24, 2015 at 12:48

Nyamiou The Galeanthrope · Accepted Answer · 2015-04-24 12:47:17Z

1

You need to create a new carList for each auto, if you reuse the same every auto is going to have the same list of cars.

answered Apr 24, 2015 at 12:47

Nyamiou The Galeanthrope

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Comments

Stefan · Accepted Answer · 2015-04-24 12:49:37Z

0

You need to fill carList for every auto. That means your service/method needs to accept a type parameter that returns all Car objects for that type, and you have to call it from within your loop over autos.

for (Auto auto : autos) {
  AutoCar ac = new AutoCar();
  ac.setType(auto.getType());
  ac.setCars(carService.getCarsByType(auto.getType())); //<-- your service/method call here
  acList.add(ac);
}

answered Apr 24, 2015 at 12:49

Stefan

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2 Comments

FakirTrappedInCode Over a year ago

I accept this Answer. But I am actually struck on iterating and using the object in Hibernate which is more of a transnational issue I will have to resolve. Thanks.

Stefan Over a year ago

That is different from what you initially asked, maybe you should ask it in a new question.

Sridhar · Accepted Answer · 2015-04-24 12:49:01Z

0

You are fetching carList only once and setting the same carList in the iterations. Fetch carList according to car type every time then set it accordingly.

answered Apr 24, 2015 at 12:49

Sridhar

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