Java initialize 2d arraylist

Question

I want to do 2D dynamic ArrayList example:

[1][2][3]
[4][5][6]
[7][8][9]

and i used this code:

 ArrayList

        

Answer 1

Use

group.add(new ArrayList(Arrays.asList(1, 2, 3)));

The ArrayList has a Collection parameter in the constructor.

If you define the group as

List> group = new ArrayList<>();
group.add(Arrays.asList(1, 2, 3));