What does it mean for a non generic class to extend a generic class

Question

public class B extends C  {

}

What does this mean? That C needs to extend A? What extra restriction am I putting instead of just saying B ext

Answer 1

You are defining a class B that inherits from class C, parameterized with type A. A must be a class or interface.

E.g.

class MyStringList extends ArrayList

means that MyString IS AN ArrayList that will only contain String elements. This class could then define e.g. a concatenate() method that returns the concatenation of all Strings in the list.

Because of this inheritance, you will be able to assign an instance to a List variable:

List strings = new MyStringList();

But you will not be able to assign it to List type variables with other parameters:

List