What is a wildcard in Java generics?

Can you explain what a wildcard is in Java generics?

Sure! A wildcard in Java generics is represented by the question mark (?) and is used to denote an unknown type.

What are the different types of wildcards?

There are three types of wildcards: unbounded wildcards, upper bounded wildcards (using extends), and lower bounded wildcards (using super).

Can you give me an example of each type?

Of course! For unbounded, you can use List<?>. For upper bounded, List<? extends Number> allows any subclass of Number. For lower bounded, List<? super Integer> allows Integer and its superclasses.

When should I use wildcards?

Use wildcards when you want to relax the restrictions on a generic type, especially when dealing with methods that can accept multiple types.