java - Nested Generics with Wildcards

Question

Why does this work:

List<?> list = new LinkedList<Integer>();

while this gives a type dismatch error:

List<List<?>> list = new LinkedList<List<Integer>>();

Why is this? Ist there a way around this, without using raw types?

Answer 1

Try

List<? extends List<?>> list = new LinkedList<List<Integer>>();

Note: you should be aware that when you use a collection like List you will only be able to use it in "read only" mode (except for adding null values).