Fancy generics capture collision

Question

Please give me a hint as to what is going on here:

List a = new ArrayList();
List b = new Array         


        

Answer 1

PECS (producer-extends, consumer-super)

• You cannot put anything into a type declared with an EXTENDS wildcard except for the value null, which belongs to every reference type
• You cannot get anything out from a type declared with an SUPER wildcard except for a value of type Object, which is a super type of every reference type