Java generics - How do I read this: Foo<T extends Bar<? extends Foo<T>>>?

Question

I am bringing myself up to date with Java generics (having worked for a loooong time on legacy code with JDK 1.4... 1.3 even) and I don't quite understand this:

public class Foo<T extends Bar<? extends Foo<T>>> { ...

Where Foo and Bar are two generic classes.

How is this to be understood because I don't quite get it?

I've read a lot about Java generics but this is a little mind bending (at least for me as a beginner).