Creating an instance of an array of objects class in Java

Question

I'm new to Java, and I'm getting an error in my main function when I try to create an instance of a DeckofCards class. The DeckofCards class is supposed to be a private array of "Cards" objects. I think my issue is something in the DeckofCards class, for some reason it's not an array I think? Maybe I created it wrong?

The errors in my main are '(' or '[' expected and array required but DeckofCards found

Here is my main function:

public static void main(String[] args) {

        Card myCard = new Card(13,1);
        System.out.println(myCard.getSuit());
        System.out.println(myCard);
        DeckofCards myDeck = new DeckofCards;  //error here
        for(int i=0; i<53; i++) {
            System.out.println(myDeck[i]); //second error here
        }
    }

Here is my DeckofCards class:

public class DeckofCards {

    private Card[] deck = new Card[52];

    public DeckofCards(){
        int i = 0;

            for(int s = 1; s<5; s++){
                for(int r = 1; r<14; r++){
            deck[i].rank = r;
            deck[i].suit = s;
            i++;

    }
}
    }
}

If anyone can tell me if I'm missing some syntax or something that'd be great! Thank you.

"for some reason it's not an array I think" - Well you just about hit the nail on the head. Use methods to interact with the Card array in your deck class. — Azar
– Azar, Commented Apr 20, 2014 at 22:51
Note: to construct an object (or actually set its parameters) you need to call a constructor. A constructor is a method of your class (even if you do not write your own constructor explicitely, Java will provide a default constructor for the class.) Now you actually wrote your constructor (public DeckOfCards()) in your class, and see: it is a method. To call a method in Java you need to type methodName(arguments). The parentheses are obligatory and arguments are not (for example, the constructor you wrote takes no arguments). — 3yakuya
– 3yakuya, Commented Apr 20, 2014 at 22:58
Can someone explain why System.out.println(myDeck[i]) returns an error? System.out.println(myCard) returns the card ("Ace of Spades" for example) and isn't myDeck[i] just a card? — singmotor
– singmotor, Commented Apr 21, 2014 at 1:04

Ted Hopp · Accepted Answer · 2014-04-20 22:52:50Z

5

You need to call the constructor:

DeckofCards myDeck = new DeckofCards(); // note parens!

In Java, the parentheses are required.

In the constructor, you will also need to initialize each element of the array to a new Card object:

for(int s = 1; s<5; s++){
    for(int r = 1; r<14; r++){
        deck[i] = new Card();
        deck[i].rank = r;
        deck[i].suit = s;
        i++;

answered Apr 20, 2014 at 22:52

Ted Hopp

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2 Comments

singmotor Over a year ago

Thanks Ted! Can you also explain why System.out.println(myDeck[i]) returns an error? println(myCard) prints out the card value ('Four of Clubs") so shouldn't that last for loop print out the values of all the cards?

Ted Hopp Over a year ago

@Acoustic77 - The variable myDeck is not an array, so you can't access parts of it using array subscripting. If you want to print the i-th card in the deck, you'll need a getter method in DeckofCards (for instance: public Card getCard(int i) { return deck[i]; }). Then you could try System.out.println(myDeck.get(i));.

TNT · Accepted Answer · 2014-04-20 22:55:05Z

3

Replace

DeckofCards myDeck = new DeckofCards;

with

DeckofCards myDeck = new DeckofCards();

and myDeck was never initialized to be an array.

answered Apr 20, 2014 at 22:55

TNT

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Comments

Reimeus · Accepted Answer · 2014-04-21 02:33:50Z

3

The error is pretty clear, myDeck is a single custom Object rather than an array

DeckofCards myDeck = new DeckofCards();  // parenthesis here
for (int i=0; i<53; i++) {
    System.out.println(myDeck); // no brackets here
}

Although the loop itself should be located within the toString method of the DeckofCards class.

edited Apr 21, 2014 at 2:33

answered Apr 20, 2014 at 22:52

Reimeus

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Comments

Robert Moskal · Accepted Answer · 2014-04-21 01:50:04Z

1

In order to iterate through the DeckofCards you'll want to expose that private Card[] array. You can use the bean notation getCards() or just make the array public.

    public class DeckofCards {

        private Card[] deck = new Card[52];

        public DeckofCards(){
            int i = 0;

                for(int s = 1; s<5; s++){
                    for(int r = 1; r<14; r++){
                deck[i].rank = r;
                deck[i].suit = s;
                i++;

        }
      } 
    }
     public Card[] getCards(){

          return deck;

     }
   }

I would probably just make the deck public.

edited Apr 21, 2014 at 1:50

answered Apr 20, 2014 at 22:57

Robert Moskal

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