Java Generics (Wildcards)

Question

I have a couple of questions about generic wildcards in Java:

1. What is the difference between List and List

Answer 1

In your first question, and are examples of bounded wildcards. An unbounded wildcard looks like , and basically means . It loosely means the generic can be any type. A bounded wildcard ( or ) places a restriction on the type by saying that it either has to extend a specific type ( is known as an upper bound), or has to be an ancestor of a specific type ( is known as a lower bound).

The Java Tutorials have some pretty good explanations of generics in the articles Wildcards and More Fun with Wildcards.