What are wildcards in Java generics?

Can you explain what wildcards are in Java generics?

Sure! Wildcards in Java generics are used to represent an unknown type. They are denoted by the question mark '?'.

What are the different types of wildcards?

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

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 each type of wildcard?

Use unbounded when you don't care about the type, upper-bounded when you need to read items of a specific type, and lower-bounded when you need to write items of a specific type.