I am wondering how I can create an array list of classes that extend certain abstract class. Lets say I have abstract class:
abstract class Product{
}
and some class that extends it:
public class Toy extends Product{
}
public class TV extends Product{
}
I would like to implement a list of classes that extend abstract class Product. How can I do that?
You need:
final List<Product> list = new ArrayList<>();
This means that you have a List of types that extends or implements Product.
You should not use:
List<? extends Product> list = new ArrayList<>();
Because list.add will be a compilation error.
It this what you are looking for?
List<? extends Product> list
List<Product> will also work in every case - the ? extends is not necessary in this case. This is only necessary in a method receiving a List of a specific type.
? extends is most likely harmful in this case.
<T extends Product> which is much better or just List<Product> as @BoristheSpider suggested.List<Toy> or a List<TV>, and you not knowing which you have. In this case, it is certainly the wrong approach, as the OP wants a List than can contain both Toy and TV.