How do I return an array from a method?

Question

I'm trying to create a deck of cards for my homework. Code is posted below. I need to create
four sets of cards (the four suits) and am create a multidimensional array. When I print the results instead of trying to pass the array, I can see that the data in the array is as expected. However, when I try to pass the array card , I get an error cannot find symbol . I've got this modeled after texbook and Java tutorial examples, and I need some help figuring out what I'm missing. I've over-documented to give an idea of how I'm thinking this SHOULD work...please let me know where I've gone horribly wrong in my understanding.

import java.util.*;
import java.lang.*;
//
public class CardGame
{
    public static int[][] main(String[] args)
    {
        int[][] startDeck = deckOfCards();  /* cast new deck as int[][], calling method deckOfCards
        System.out.println(" /// from array: " + Arrays.deepToString(startDeck));
    }

    public static int[][] deckOfCards()   /* method to return a multi-dimensional array */
    {
        int rank;
        int suit; 
        for(rank=1;rank<14;rank++)    /* cards 1 - 13 .... */
        {
            for(suit=1;suit<5;suit++)  /* suits 1 - 4 .... */
            {
                int[][] card = new int[][]    /* define a new card...  */
                {
                    {rank,suit}      /* with rank/suit from for... loops */
                };
                System.out.println(" /// from array: " + Arrays.deepToString(card));
             }
         }
         return card;  /*  Error: cannot find symbol 
    }
}

Answer 1

card only exists within the for loop: variables are only valid within the block ( {..} ) within which they are declared.

Note rules for the main() method (from section 12.1.4 Invoke Test.main of JLS 3.0 ):

The method main must be declared public, static, and void. It must accept a single argument that is an array of strings.

Answer 2

Ahh... Scope is your issue... Look where card is declared relative to where it is returned from. Remember when you declare a variable within a loop or sub function its scope is limited to that location on the stack.. If this doesn't help message me back.

Answer 3

The reference card is limited to the scope of your inner for loop. A variable only exists inside of the inner most set of braces {} that enclose it.

You want to make one array, outside the loop, and fill it up in the loop. Not make a totally new array for each pass of the loop.

Answer 4

Your card was defined in the for loop. Try with it defined at the top, otherwise it gets redefined every loop, and your function will return null.

import java.util.*;
import java.lang.*;
//
public class CardGame
{
    public static int[][] main(String[] args)
    {
        int[][] startDeck = deckOfCards();  /* cast new deck as int[][], calling method deckOfCards
        System.out.println(" /// from array: " + Arrays.deepToString(startDeck));
    }

    public static int[][] deckOfCards()   /* method to return a multi-dimensional array */
    {
        int rank;
        int suit; 
        int[][] card = new int[][]    /* define a new card...  */
        for(rank=1;rank<14;rank++)    /* cards 1 - 13 .... */
        {
            for(suit=1;suit<5;suit++)  /* suits 1 - 4 .... */
            {

                {
                    {rank,suit}      /* with rank/suit from for... loops */
                };
                System.out.println(" /// from array: " + Arrays.deepToString(card));
             }
         }
         return card;  /*  Error: cannot find symbol 
    }
}

Answer 5

Thanks to everyone who pointed out scope as my issue...that was definitely it. Here's my revised code, which I'm happy to report works fantastically.

import java.util.*;
import java.lang.*;
//
public class CardGame 
{
    static int card[][];   /* card is now a global variable...and static so it can */
                           /* interact with static methods.  */
//
    public static void main(String[] args)
    {
        int card[][];
        int[][] startDeck = deckOfCards();
        System.out.println(" /// from array: " + Arrays.deepToString(startDeck));
    }


    public static int[][] deckOfCards()
    {
        int rank;
        int suit;
        for(rank=1;rank<14;rank++)
        {
            for(suit=1;suit<5;suit++)
            {
                card = new int[][]
                {
                    {rank,suit}
                };
                System.out.println(" /// from array: " + Arrays.deepToString(card));
             }
         }
         return card;
    }   
}