Understanding wildcards in Java generics

Question

I\'m not sure why the last statement in the following code is illegal. Integer should be a subtype of ?, so why can\'t I assign it to b

Answer 1

The reference "b" is declared as a List, that is, a "List of something I don't know yet". You can assign pretty much any implementation to this reference, like a List. This is why it is forbidden to add anything to the lists through this reference.