generics - What does Map<?, ?> mean in Java?

Question

What does Map<?, ?> mean in Java?
I've looked online but can't seem to find any articles on it.

edit : I found this on MP3 Duration Java

Answer 1

Map<?,?> means that at compile time, you do not know what the class type of the key and value object of the Map is going to be.

Its a wildcard type. http://download.oracle.com/javase/tutorial/extra/generics/wildcards.html