Is it possible to split a integer arraylist in half into 2 separate arraylists?

Question

public class War {

    public static void main(String args[])
    {
            ArrayList<Integer> deck = new ArrayList<>(List.of(2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 
            5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 
            12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14));
        
            // Creates a deck and shuffles it
            Collections.shuffle(deck);
    
            System.out.println(deck);
    
            ArrayList<Integer> player1 = new ArrayList<>();
            ArrayList<Integer> player2 = new ArrayList<>();
    
            System.out.println(player2);
            System.out.println(player1);  
    }    
}

This is for my card war game where I want to split the deck arraylist in half (2 lists) and then be able to use those 2 lists as the cards for the 2 players.

Does *half* mean half of the size/length or do the values matter anyhow, maybe in addition? — deHaar, Jan 06 '22 at 06:30
Splitting the deck clean in half, or dealing out the deck to two players? — Chris, Jan 06 '22 at 06:54

Eran · Answer 1 · 2022-01-06T07:24:55.460

You can use subList:

List<Integer> deck1 = deck.subList(0,deck.size()/2);
List<Integer> deck2 = deck.subList(deck.size()/2,deck.size ());

Note that these are views of the original List, so changes in these sub-llsts will be reflected in the original List.

If you want to avoid that, you can make copies:

List<Integer> deck1 = new ArrayList<>(deck.subList(0,deck.size()/2));
List<Integer> deck2 = new ArrayList<>(deck.subList(deck.size()/2,deck.size ()));

Or, as Basil commented, if you wish the lists to be immutable, use:

List<Integer> deck1 = List.of(deck.subList(0,deck.size()/2));
List<Integer> deck2 = List.of(deck.subList(deck.size()/2,deck.size ()));

And for a unmodifiable list, use `List.of` like this: `List.of ( deck.subList( 0 , deck.size() / 2 ) )`. — Basil Bourque, Jan 06 '22 at 07:01

Is it possible to split a integer arraylist in half into 2 separate arraylists?

1 Answers1