Question

I have this interface and classes:

interface I {
    void method1();
}
class A implements I  {
    void method1(){
    ....
    }
}

Assume I have this list: List<A> aslist filled with A items, and I have a variable of type List<I> vari=null;
I need ti do vari=aslist? How can I do it with the minimum convertions?

Answer 1

You can’t. A List<Car> is not a List<Vehicle>. If it was, you could do the following:

List<Car> cars = new ArrayList<Car>();
List<Vehicle> vehicles = (List<Vehicle>) cars;
cars.add(new Bicycle());

and it would thus completely break the type-safety of the collection.

What you can do is the following:

List<? extends Vehicle> vehicles = cars;