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My goal is to have a list of cars as an Object so that, I can retrieve a Car from that list. As well as get details of the cars. Can someone point me to the right direction

What I have done so far.

  1. Create a class called Car and have the variables CarNum, carName, carPlate;
  2. generated getters and setters for the variables and a toString as the carName
  3. Create a class called CarCollection as follows

. 

 public class CarCollection {
        private List<CarItem> mCarList;



        public void addVan(CarItem v) {
            mCarList.add(v);
        }

        public List<CarItem> getCarList() {
            return mCarList;
        }

The following test doesn't work. Why? 

public class TestCarCollectionprocess {

    public static void main(String[] args) {

        CarItem car1 = new CarItem();
        car1.setmCarName("Pedro");
        car1.setmCarNum(1);

        CarItem car2 = new CarItem();
        car2.setmCarName("Rene");
        car2.setmCarNum(2);

        CarCollection carList = new CarCollection();        
        carList.addCar(car1);
        carList.addCar(car2);
        System.out.println(carList.getCarList());
    } 
}
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4
  • 1
    What doesn't work exactly? Commented Apr 28, 2016 at 18:51
  • please provide what you got in output. Commented Apr 28, 2016 at 18:52
  • I don't see an addCar method in your CarCollection class and I don't see if you are fully constructing the private List<CarItem> mCarList; Commented Apr 28, 2016 at 18:53
  • 1
    Your should READ the exception you get. It tells exactly what and where the problem is. stackoverflow.com/questions/218384/… Commented Apr 28, 2016 at 19:04

2 Answers 2

Reset to default
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What I see from your code, you should get NullPointerException in addVan method since you didn't initialize List, so change it like this:

 private List<CarItem> mCarList = new ArrayList<>();
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1 Comment

Thanks. This was the answer I was looking for!
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You are trying to add a CarItem to the CarCollection's mCarList without ever instantiating the list so you should be getting a null reference exception. In your carCollection class, create a constructor that sets 

mCarList = new List<CarItem>();
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1 Comment

no, IList is an interface, List is an implementation of the interface

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