CODEWITHSUNDEEP
java
MrD
MrD

Reputation: 5086

Shuffling deck algorith

I have the following java code, which is supposed to "shuffle" cards in a deck. The deck is an arraylist containing card objects.

private void ShuffleDeck() {
    //Number of cards in deck
    int deckSize = deck.size();

    //Swapping 100 cards
    for(int i = 0; i < 15; i++) {

        //Generating two random card indexes
        int indexA = (int) ((Math.random() * deckSize-1));
        int indexB = (int) (Math.random() * deckSize-1);
        System.out.println(indexA + " " + indexB);

        //Getting objects
        Card cardA = deck.get(indexA);
        Card cardB = deck.get(indexB);

        //Temporaily removing these cards from deck
        deck.remove(cardA);
        deck.remove(cardB);

        //Swapping around the two cards
        deck.add(indexA, cardB);
        deck.add(indexB, cardA);

    }

}

However, when I run this method some cards seem to "disappear" from the deck... Any suggestions as to why this is? :)

Upvotes: 0

Views: 176

Answers (1)

wchargin
wchargin

Reputation: 16037

Assuming deck is a List<Card> (including ArrayList, etc.):

public void shuffleDeck() { // please use camelCase method names
    Collections.shuffle(deck);
}

Don't reinvent the wheel.

Upvotes: 9

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