Simple card game, letting user chose amount of decks in the game

Question

Instead of translating I've added comment in the code. But its mainly strings that are in Swedish.

I have trouble adding a feature where the game asks the user the amount of decks (each deck containing the standard 52 cards.)

Just like how the game ask if the deck should be shuffled or not the user should be asked how many decks the game should contain, the rest can be as it is for now.

I've tried (but ofc it didnt work):

   int n = //amount of decks

int[] deck = new int[52*n];

Here is the program:

import java.util.Scanner;

public class KortSpel {
    public static void main(String[] args) {
        Boolean fortsatt = true;        
        while(fortsatt){    

        Scanner scan = new Scanner(System.in);

        int[] deck = new int[52]; 

        String[] suits = {"Hjärter", "Spader", "Ruter", "Klöver"};    //the suits
        String[] ranks = {"Ess", "2", "3", "4", "5", "6", "7", "8", "9", "10", "Knäckt", "Drottning", "Kung"}; //the rank of the cards

        for( int i = 0; i < deck.length; i++) deck[i] = i;



        System.out.print("Skriv dra för att dra korten annars avsluta."); //ask the user if he want to keep playing or not
        String svar2 = scan.nextLine();

        if (svar2.equalsIgnoreCase("Avsluta")){ 
            fortsatt = false;
            System.out.println("Du har nu avslutat.");  //tells the user he has exit
        }

        else {


            System.out.print("Vill du bland korten? (ja/nej) "); //ask the user if he want to shuffle the cards Y/N
            String svar = scan.nextLine();

            if (svar.equalsIgnoreCase("ja")) {                  // if shuffled

                for( int i = 0; i < deck.length; i++) {

                    int index = (int)(Math.random() * deck.length);
                    int temp = deck[i];
                    deck[i] = deck[index];
                    deck[index] = temp;
                }
                for( int i = 0; i < 52; i++) {
                    String suit = suits[deck[i] / 13];
                    String rank = ranks[deck[i] % 13];
                    System.out.println("Kort nummer " + deck[i] + ": " + suit + " " + rank);
                }
            }

            else    {                                           //if not suffled

                for( int i = 0; i < deck.length; i++) deck[i] = i;

                for( int i = 0; i < 52; i++) {
                    String suit = suits[deck[i] / 13];
                String rank = ranks[deck[i] % 13];
                System.out.println("Kort nummer " + deck[i] + ": " + suit + " " + rank);
        }
        }

    }
}       
}
}

All help is appreciated and since Im not very good with java, simplicity is preferred.

Thanks in advance!

Answer 1

All this gets a lot easier if you take up a formal Object Oriented model instead of informally defining a card.

What is a card? In this context, that's rather simple; it's a pair of values, one of which is a suit, and the other is a rank. So long as the suit and rank are both valid, both are cards. This gives us the following class:

public class Card{
    public final String suit;
    public final String rank;

    public Card(String s, String r){
        suit = s;
        rank = r;
    }
}

Before we go further, I would like to note here that using the type String for suit and rank is not a great idea; both have a finite set of potential values and as such can be better represented as an enumerated type (or Enum). We can define the Enums like this (though obviously you could change the words to be swedish):

public enum Suit{
    HEARTS,
    SPADES,
    CLUBS,
    DIAMONDS
}

public enum Rank{
    ACE,
    TWO,
    THREE,
    FOUR,
    FIVE,
    SIX,
    SEVEN,
    EIGHT,
    NINE,
    TEN,
    JACK,
    QUEEN,
    KING
}

Which changes our Card class to look like this:

public class Card{
    public final Suit suit;
    public final Rank rank;

    public Card(Suit s, Rank r){
        suit = s;
        rank = r;
    }
}

From here, creating a deck class is easy:

public class Deck{
    private ArrayList<Card> deck; //An array of cards that represents this deck.

    public Deck(){
        deck = new ArrayList<Card>();

        //For every combination of suit and rank, create and add a card to this deck
        for(Suit s : Suit.values()){
            for(Rank r : Rank.values()){
                deck.add(new Card(s, r));
            }
        }
    }
}

From here you can add functionality to the deck class for shuffling, drawing cards, etc. For your original question, creating multiple decks is just a question of creating many single decks and adding all of their contents together. We can create a constructor that does that, and add that to our deck class:

public class Deck{
    private ArrayList<Card> deck; //An array of cards that represents this deck.

    public Deck(){
        deck = new ArrayList<Card>();

        //For every combination of suit and rank, create and add a card to this deck
        for(Suit s : Suit.values()){
            for(Rank r : Rank.values()){
                deck.add(new Card(s, r));
            }
        }
    }

    /** Creates a deck that is the sum of all the cards in the input deck(s) */
    public Deck(Deck... decks){
        deck = new ArrayList<Card>();
        for(Deck d : decks){
            deck.addAll(d.deck);
        }
    }
}