Thread: Shuffling a deck

So I have all this made.. and I need to shuffle the deck, but it's not working and it's getting on my nerves...

 
import java.util.*;
 
class Hand { 
    static Card[] deck = new Card[52];
    Card[] hand = new Card[10];
    static int index;
 
 
 
 
    public static void createDeck () {
        int m = 0;
        for (int j = 0; j < 4; j++) {
            for (int k = 1; k < 14; k++) {
               deck[m] = new Card(j,k);
               m++;
            }
        }
        index = 0;
    } //end createDeck
 
    public static Card deal () {
        index++;
        return deck[index-1];
    } //end deal
 
 
 
    public static int compareCard (Card c1, Card c2) {     
        if (c1.getSuit() > c2.getSuit()) return 1; 
        if (c1.getSuit() < c2.getSuit()) return -1;
        if (c1.getRank() > c2.getRank()) return 1; 
        if (c1.getRank() < c2.getRank()) return -1;
        return 0;
    } //end compareCard
 
    public void printDeck (int size) {
        int j = 0;
        while (j < size) {
            deck[j].printCard();
            j++;
        }
    }//end printDeck
 
    public void shuffleDeck () {
         Random randomNumber = new Random ();
 
        for (int i =0; i < deck.length; i++) {
            int randomInt = randomNumber.nextInt (53);
          Card temp = hand [i];
           hand[i] = hand [randomInt];
           hand[randomInt] = temp;
 
    }
}//end shuffleDeck
 
} //end class

OK.

You read these stack traces from the top down, until you reach a line of your code (which happens rather soon here!). It is saying that the problem is an ArrayIndexOutOfBoundsException. In other words you are trying to access an array at a crazy place (say a negative index, or an index that is too big.)

That ## number is the crazy index that the Java runtime is complaining about. Not all exception messages are as helpful.

Now the problem is evidently occurring at the line "hand[i] = hand [randomInt];" which is line 52 of the file Hand.java.

The first thing to do is have a look where the hand array is initialised. That's up near the top:

Card[] hand = new Card[10];

So hand is an array that holds exactly ten cards. But back where the problem is occuring you say:

int randomInt = randomNumber.nextInt (53);
Card temp = hand [i];
hand[i] = hand [randomInt];

If randomInt is ever bigger than nine (and it very well may be) then you will get an ArrayIndexOutOfBoundsException.

Basically the hand is too small (ten elements) for what you are shuffling (a random thing 0->52). I wonder if you mean to shuffle the hand or the deck...