Working with arrays of lists pattern in java

Question

I am writing a card game in java where I need to spread cards from a deck into several columns until I have fixed amount of cards left. This is how I do this.

public class Column extends ArrayList {}
List deck = Cards.createNewDeck();
Column[] columns = new Column[10];
int c = 0;

while (deck.size() > 50) {
    if (c == 10) {
        c = 0;
    }
    if (columns[c] == null) {
        columns[c] = new Column();
    }
    columns[c].add(Cards.dealTopCard(deck));
    c += 1;
}

This somehow seems clunky. Is there a more readable/comprehensive way of doing the same thing?

Jack · Accepted Answer · 2010-03-26 04:42:26Z

1

public class Column extends ArrayList {}
List deck = Cards.createNewDeck();
Column[] columns = new Column[10];
int c = 0;

for (int i = 0; deck.size() > 50; i = (i+1)%10)
{
  if (columns[i] == null)
    columns[i] = new Column();

  columns[i].add(Cards.dealTopCard(deck));
}

The modulo (%) operator gives the remainder of the integer division between the two numbers effectively giving you a number that goes back to 0 when reaching 10.

By the way you should decide: use a bidimensional array or just ArrayLists, don't mix things.

Then since generics do exist, use them instead that extending classes: that's what parametric polymorphism is for! Something like:

ArrayList<Int, ArrayList<Card>> columns = new ArrayList<ArrayList<Card>>();

edited Mar 26, 2010 at 4:42

answered Mar 26, 2010 at 4:36

Jack

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2 Comments

Mad Wombat Over a year ago

Well, array of lists seemed to be the best approach. I have a fixed number of columns, but I don't know how many cards will be in each column. A list of lists is a bit more verbose (columns[i] vs. columns.get(i)). Your example is nice, but I was looking for something more profound. In clojure I would write something like (def columns (partition 10 10 (list) (take 54 (create-deck)))

Jack Over a year ago

Unfortunately this is Java, not Clojure :) Verbosity is quite part of the game.

polygenelubricants · Accepted Answer · 2010-03-26 04:36:24Z

0

Don't use raw types.
Don't mix arrays with lists.

My suggestion is to define List<Pile<Card>> columns, where Pile<Card> has a List<Card>.

Then define a dealer type that converts a Deck<Card> into multiple Pile<Card>. That makes it easier to plug in different deck-to-piles strategies just in case.

answered Mar 26, 2010 at 4:36

polygenelubricants

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