How can i Randomize Unique Numbers in Java [duplicate]

Question

So i'm making a game where i have to randomize 52 numbers from 1 to 52 so the order has to change i use this

    class Deck
{
    Random r = new Random();
    int[] Card = new int[52];
}

Answer 1

you fill in the array from 1 to 52

for(int i=0;i<52;i++)Card[i]=i+1;

and then you shuffle it:

for(int i=1;i<52;i++){
    int randIndex = r.nextInt(i+1);
    int tmp = Card[i];
    Card[i] = Card[randIndex];
    Card[randIndex]=tmp;
}

Answer 2

Since you are building and shuffling a deck of cards I will point you to the java 1.5 Enum tutorial. It uses enums to build up a Collection of cards and then uses Collections.shuffle() to randomize the deck.

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

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

    private final Rank rank;
    private final Suit suit;
    private Card(Rank rank, Suit suit) {
        this.rank = rank;
        this.suit = suit;
    }

    public Rank rank() { return rank; }
    public Suit suit() { return suit; }
    public String toString() { return rank + " of " + suit; }

    private static final List<Card> protoDeck = new ArrayList<Card>();

    // Initialize prototype deck
    static {
        for (Suit suit : Suit.values())
            for (Rank rank : Rank.values())
                protoDeck.add(new Card(rank, suit));
    }

    public static ArrayList<Card> newDeck() {
        return new ArrayList<Card>(protoDeck); // Return copy of prototype deck
    }
}

This builds your deck. The following then shuffles with Collections.shuffle() and deals some cards.

public class Deal {
    public static void main(String args[]) {
        int numHands = Integer.parseInt(args[0]);
        int cardsPerHand = Integer.parseInt(args[1]);
        List<Card> deck  = Card.newDeck();
        Collections.shuffle(deck);
        for (int i=0; i < numHands; i++)
            System.out.println(deal(deck, cardsPerHand));
    }

    public static ArrayList<Card> deal(List<Card> deck, int n) {
         int deckSize = deck.size();
         List<Card> handView = deck.subList(deckSize-n, deckSize);
         ArrayList<Card> hand = new ArrayList<Card>(handView);
         handView.clear();
         return hand;
     }
}