How to create an 2D ArrayList in java? [duplicate]

Answer 1

1st of all, when you declare a variable in java, you should declare it using Interfaces even if you specify the implementation when instantiating it

ArrayList> listOfLists = new ArrayList>();

should be written

List> listOfLists = new ArrayList>(size); 

Then you will have to instantiate all columns of your 2d array

    for(int i = 0; i < size; i++)  {
        listOfLists.add(new ArrayList());
    }

And you will use it like this :

listOfLists.get(0).add("foobar");

But if you really want to "create a 2D array that each cell is an ArrayList!"

Then you must go the dijkstra way.