Convert 2D ArrayList of Integers to multiple ArrayLists of Integers?

Question

I have a 2D ArrayList:

List<List<Integer>> list = new ArrayList<List<Integer>>();

And I want to go through a for loop and convert each line of the list to a new ArrayList:

for (int i = 0; i < list.size(); i++) {
        ArrayList<Integer> element = list.get(i);
}

This spits out the error

incompatible types: java.lang.Object cannot be converted to java.util.ArrayList

I don't use 2D ArrayLists very often. Say my list is

[[1, 2, 3], [0, 5], [-2], [2, 3, 1]]

How can I assign each block to an ArrayList? I want to first have an ArrayList that is [1, 2, 3], send it to a function, then rinse and repeat for the rest of the list.

Answer 1

get() method always return object of type Object class. You have to downcast it :

ArrayList<Integer> element = ( ArrayList<Integer>)list.get(i);