Question

How to print ArrayList from HashMap?

Map<String, ArrayList<Car>> cars = new HashMap<String, ArrayList<Car>>;

ArrayList<Car> carList = cars.get("bmw");

    for (int i = 0; i < carList.size(); i++) {
        System.out.println(carList.get(i));
    }

The code causes:

java.lang.NullPointerException

Despite the “bmw” key exists and is populated.

Answer 1

Try adding in a

System.out.println(cars.get("bmw"));

to check and see what exactly is in it (in the Map, and the ArrayList of cars).