如何在桥牌游戏的Card Deck shuffle（）中切换纸牌位置

Question

So first of all I have a deck which has numbers 2-14 as Clubs or [0]-[12] in the Card [] object, and values(rank) 2-14 so on for Diamonds [13]-[25], Hearts [26]-[38], Spades [39]-[51].

I then have to shuffle these cards with their given values by using Math.random() inside a shuffle() class such as...

//Holds an array of card objects
private Card [] cards  = new Card [52];

//Holds number of cards remaining in deck
private int count;

public Deck()
{
    for (int i = 0; i <= 12; i++) {
        cards[i] = new Card(i+2, 'C');
        count = 52-13;
    }

    for (int i = 13; i <= 25; i++) {
        cards[i] = new Card(i-13+2, 'D');
        count = 39-13;
    }

    for (int i = 26; i <= 38; i++) {
        cards[i] = new Card(i-26+2, 'H');
        count = 26-13;
    }

    for (int i = 39; i <= 51; i++) {
        cards[i] = new Card(i-39+2, 'S');
        count = 13-13;
    }
}

public void shuffle()
    {
        for (int i = 0; i <= 51; i++)
            if (i <= 12) 
                cards[i] = new Card((int)(Math.random() * 52), 'C');
            else if (i <= 25) 
                cards[i] = new Card((int)(Math.random() * 52), 'D');
            else if (i <= 38) 
                cards[i] = new Card((int)(Math.random() * 52), 'H');
            else if (i <= 51) 
                cards[i] = new Card((int)(Math.random() * 52), 'S');


    }

This changes the values for the numbers 2-14 as random integers from 0-51, the only part I don't understand is how to take that random integer which replaces my values 2-14 and have it so that if (as example) card[14] = 35 THEN swap card[14] with card[35]. I have no experience with using Collections or ArrayList.

Answer 1

In shuffle(), you don't actually want to create new cards, just swap them. I would suggest using (int)(Math.random() * 52) to choose the value of the array index and then use a temp variable to perform the swap.

public void shuffle()
{ // replace 51 with any arbitrary number
  for (int i = 0; i <= 51; i++) {
    // two cards to swap
    int j = (int)Math.floor(Math.random() * 52);
    int k = (int)Math.floor(Math.random() * 52);

    // swap cards
    Card temp = card[j];
    card[j] = card[k];
    card[k] = temp;
  }
}

Hope that helps.