Why does this not compile : List> lss = new ArrayList>(); [duplicate]

Answer 1

Same reason

List<List> myList = new ArrayList<ArrayList>();

wont work.

You can see this question for more details.

Answer 2

The problem is that type specifiers in generics do not (unless you tell it to) allow subclasses. You have to match exactly.

Try either:

List<List<String>> lss = new ArrayList<List<String>>();

or:

List<? extends List<String>> lss = new ArrayList<ArrayList<String>>();

Answer 3

From http://docs.oracle.com/javase/tutorial/java/generics/inheritance.html

Note: Given two concrete types A and B (for example, Number and Integer), MyClass<A> has no relationship to MyClass<B>, regardless of whether or not A and B are related. The common parent of MyClass<A> and MyClass<B> is Object.