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

Don't use the ? wildcard. It means "Some specific type I don't know", and since you don't know the type, you can't add anything to the list. Change your code to use List and everything will work.

This is fast becoming the most frequently asked Java question, in a hundred variations...