Question about the Deck class in the Sun tutorial.

[Brian Pianczk]

import java.util.*;

public class Deck {

    public static int numSuits = 4;
    public static int numRanks = 13;
    public static int numCards = numSuits * numRanks;

    private Card[][] cards;

    public Deck() {
        cards = new Card[numSuits][numRanks];
        for (int suit = Card.DIAMONDS; suit <= Card.SPADES; suit++) {
            for (int rank = Card.ACE; rank <= Card.KING; rank++) {
                cards[suit-1][rank-1] = new Card(rank, suit);
            }
        }
    }

    public Card getCard(int suit, int rank) {
        return cards[suit-1][rank-1];
    }
}
    

Having just gone through the section on Arrays, again is this how this bit of code is working?

 [numSuits]    [numRanks]
going down?   going across?

DIAMONDS   ACE TWO THREE FOUR . . .
SPADES     ACE TWO THREE FOUR . . .
HEARTS     ACE TWO THREE FOUR . . . 
CLUBS      ACE TWO THREE FOUR . . .   

does this loop first make the DIAMONDS column then add the 13 cards to it, then create SPADES then add cards etc...?

[Campbell Ritchie]

Difficult to be sure without seeing the whole of the code; where can you find the Card class?

You are declaring an array of arrays (not a two-dimensional array), then you instantiate it as a 4-member array, each member being a 13-member array. Then you fill in each of the 4 arrays with Cards, using the 13 ranks. Note the ranks appear to begin at 1, and arrays begin at 0, so you have to write - 1 in the array indices. There are obviously numbers in the Card class, DIAMONDS = 1 . . . CLUBS = 4, and ACE = 1 . . . KING = 13. There are probably also arrays in the Card class whereby suits[0] = "Diamonds" and ranks[0] = "Ace".

I don't think you have a "Diamonds" row anywhere, you have an array where every member is marked as "Diamonds". Very subtle difference, but you cannot get "Diamonds" out of the 4-member array. You can get "Diamonds" out of any of the Cards in the 1st 13-member array.

[amitabh mehra]

Not exactly... since you havent posted the Card class, I assume it would have final static ints defined as
DIAMONDS=1, ..., SPADES=4
ACE=1..KING=13

So now when you are creating an array of array of Card objects,think of it as a table, cards[row][column]
So cards[diamonds-1][ace-1] means cards[0][0] and this will now hold a card object that corresponds to the Ace of Diamond.

I hope this makes things a tad clear for you.

[Brian Pianczk]

Thanks to both of you. I understand now, and yes the Card class contains a private static variable for each suit, and rank.

[Campbell Ritchie]

You're welcome

[Campbell Ritchie]

If it is a private static field in the Card class, how can you access it from the Deck class?

[Brian Pianczk]

Campbell Ritchie wrote:If it is a private static field in the Card class, how can you access it from the Deck class?

Oops

  public final static int DIAMONDS = 1;