CODEWITHSUNDEEP
javaarraysfor-loopreturnindexof
suck_at_coding18
suck_at_coding18

Reputation: 41

How to get distinct different random objects in an array?

Sorry if this is long but i'm writing a program that draws a poker hand(5 different cards) from a standard deck of 52. The only part Im still struggling with is getting different cards. The code I have now is as simple as it gets and works for the most part but sometimes can draw the same card more than once. I want the card to be removed from the deck once its drawn and i'm stuck on that part.

Card[] hand = new Card[5];
        for (int i = 0; i < 5; i += 1)
        {
          int index = rand.nextInt(52);
          hand[i] = cards[index];
        }
    return hand;

Upvotes: 0

Views: 120

Answers (4)

Raman Sahasi
Raman Sahasi

Reputation: 31871

Just create a List of Integers ranging from 1 to 50. I've demonstrated this example using Java 1.8.

public class NumUtility {
    public static List<Integer> shuffle() {
        List<Integer> range = IntStream.range(1, 53).boxed()
                .collect(Collectors.toCollection(ArrayList::new));
        Collections.shuffle(range);
        return range;
    }
}

Now you can iterate through index 1 to 5 and whenever you want shuffled numbers, just call the above method.

Card[] hand = new Card[5];

//call this method whereever you want random integers.
List<Integer> range = NumUtility.shuffle();

for (int i = 0; i < 5; i += 1) {
    hand[i] = range.get(i);
}
return hand;

Upvotes: 0

ToXik-yogHurt
ToXik-yogHurt

Reputation: 111

You could literally do what you do with a deck of cards:

class Deck
{
    private LinkedList<Card> cards = new LinkedList<Card>();

    Deck()
    {
          for (i=0; i<52; ++i) {
              // or however you want to correctly create a card
              cards.add(new Card(i))
          }
    }

    public Card takeRandomCard()
    {
          int takeCard = rand.nextInt(cards.size());
          return cards.remove(takeCard);
    }
}

int handSize = 5;
Deck deck = new Deck();
Card[] hand = new Card[handSize];
for (int i=0; i<handSize; ++i) {
    hand[i] = deck.takeRandomCard();
}

This may not be the most efficient method but it's hopefully pretty clear what it's doing.

Pulling random cards may or may not be faster than shuffling the entire deck first. LinkedList is faster than ArrayList when removing random entries. Probably irrelevant though really.

Upvotes: 0

T.Tony
T.Tony

Reputation: 515

You can create a ArrayList like 

List<Card> cards = new ArrayList<>();

// add 52 cards to cards

Card[] hand = new Card[5];
for (int i = 0; i < 5; i ++) {
    int index = rand.nextInt(cards.size());
    hand[i] = cards.remove(index);
}

Upvotes: 1

kaitoy
kaitoy

Reputation: 1675

Use List and Collections.shuffle().

List<Card> cards = new ArrayList<>(52);
for (int i = 0; i < 52; i++) {
  cards.add(new Card(i)); // or so
}
Collections.shuffle(cards);

Card[] hand = new Card[5];
for (int i = 0; i < 5; i += 1) {
  hand[i] = cards.remove(0);
}

return hand;

Upvotes: 2

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