collections - ArrayList of ArrayList of ints in Java? -

i working on writing sudoku solver , want grid stored arraylist of arraylist of ints...each spot have arraylist of ints of possible numbers (or definite value).

arraylist<arraylist<int>> sudoku_board = new arraylist <arraylist<int>>(); 

java throwing me error saying "dimensions expected after token" on ints.

generic type parameters require reference types, rather primitive types. use

list<arraylist<integer>> sudoku_board = new arraylist <arraylist<integer>>(); 

also when coding interface use interface reference type, in case list. appears within generics should remain implementation type due non co-variance of generics.

from @assylias comment, more generic type of list is

list<list<integer>> list = new arraylist<list<integer>>(); 

this allow list implementations types other arraylist added should refactoring necessary later.