Question

I’m a fairly noobish guy trying to learn Java, and I’m having a little trouble completing a task I gave myself. Basicaly I’m trying to do the exercises at the end of this page.

I managed to finish it with three classes. The Card:

public class Card {

public int nRank; // Used later
public int maxRank = 13; //The max number of Ranks
public int nSuit; // Used later
public int maxSuit = 4; // Max number of suits


//Associate both rank and suit numbers with strings

public String[] ranks = new String[maxRank - 1];
{
    ranks[0] = "two";
    ranks[1] = "three";
    ranks[2] = "four";
    ranks[3] = "five";
    ranks[4] = "six";
    ranks[5] = "seven";
    ranks[6] = "eight";
    ranks[7] = "nine";
    ranks[8] = "ten";
    ranks[9] = "Jack";
    ranks[10] = "Queen";
    ranks[11] = "King";
    ranks[12] = "Ace";

    }

public String[] suits = new String[maxSuit - 1];
{
    suits[0] = "Clubs";
    suits[1] = "Diamonds";
    suits[2] = "Spades";
    suits[3] = "Hearts";
    }

public String suit = suits[nSuit]; //The suit string of the card whose suit number is nSuit
public String rank = ranks[nRank]; //Same but with ranks

//Constructor for the Card object, with two arguments, x for rank, y for suit
public Card(int x,int y){
    this.nRank = x;
    this.nSuit = y;
}

//method to get which card it is in a string
public String whatCard(){
    return rank + " of " + suit;
}
}

The Deck:

    public class Deck {

public static int nRanks = 13; //number of ranks
public static int nSuits = 4; // number of suits
public static int nCard = nRanks * nSuits; // number of cards

Card[] deck = new Card[nCard -1]; //new array called deck to store all the cards 
int h = 0; //a variable to control the place of each card in the array
//constructor for the Deck
public Deck() {

while(h < 52){ // loop until there are 52 cards

// cycles through all the possible combinations between i(ranks) and j(suits) and creates a card with each
for(int i = 1; i <= nRanks; i++){

    for(int j = 1; j <= nSuits; j++){

        deck[h] = new Card(i,j); // creation of the card
        h++; // adds 1 to to h so the program knows how many cards are there
        }
    }

}
}
//method for getting a card depending on its position in the array(x)
    public Card getCard(int x){
    return deck[x-1];   
}
}

And the displayer of the cards/deck, which I called Shuffle:

public class Shuffle {

public static void main(String[] args){
        Deck newDeck = new Deck(); // creates a new Deck object
        //loops through all the cards in the deck
    for(int i = 0; i < Deck.nCard; i++){
        System.out.println(newDeck.getCard(i).whatCard()); // prints each card
    }

}

}

Although eclipse doesn’t notice any errors in the code, when I try to compile, I’m shown this:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 12
    at Card.<init>(Card.java:26)
    at Deck.<init>(Deck.java:20)
    at Shuffle.main(Shuffle.java:5)

What have I missed?

Answer 1

ranks[] and suits[] have both indexes from 0 to 12.

you’re trying to access from 1 to 13 (in your for loop)

Use this code :

for(int i = 0; i < nRanks; i++){

    for(int j = 0; j < nSuits; j++){

        deck[h] = new Card(i,j); // creation of the card
        h++; // adds 1 to to h so the program knows how many cards are there
    }
}

EDIT :

I noticed another error, the one who generate the out of bounds :
In your Card class, change this lines :

public String[] ranks = new String[maxRank - 1];
public String[] suits = new String[maxSuit - 1];

by

public String[] ranks = new String[maxRank];
public String[] suits = new String[maxSuit];

When you create an array, you don’t specify the last index, but the place avaible. So if you wanna put 13 values, specify new String[13].

---

EDIT : the full Deck class :

public class Deck {

   public static int nRanks = 13;  
   public static int nSuits = 4; 
   public static int nCard = nRanks * nSuits; 

   Card[] deck = new Card[nCard]; //nCard indexes, not nCard - 1

   public Deck() {
      //remove the while, double loop useless
      for(int i = 0; i < nRanks; i++){
         for(int j = 0; j < nSuits; j++){
            deck[j * nRanks + i] = new Card(i,j);
         }
      }
   }

   public Card getCard(int x){
      return deck[x-1];   
   }
}