Nested Generics with Wildcards

Question

Why does this work:

List list = new LinkedList();

while this gives a type dismatch error:

List

        

Answer 1

To actually answer your question:

In the first case, "list" holds a list of one particular, unspecified type - in this case, Integer.

In the second case, "list" holds a list of lists, but each of the sublists may be of any particular type, but the following would be perfectly fine (note the types of the two lists being added):

List> list = new LinkedList>();
list.add(new LinkedList());
list.add(new LinkedList());

It's very similar to the reason why you can't do

List