ArrayList is empty but why?

I'm trying to add C开发者_C百科ards to ArrayList deck, but it doesn't seem to work(most of the code is an example on oracle.com ). I'm probably doing something really stupid, but I can't seem to find it.. this is the code:

public class Card {

    public enum Rank 
    {
        DEUCE, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE,
        TEN, JACK, QUEEN, KING, ACE
    }

    public enum Suit
    {
        HEARTS, DIAMONDS, SPADES, CLUBS
    }

    private final Rank rank;
    private final Suit suit;
    private static final List<Card> deck = new ArrayList<Card>();

    public Card(Rank rank, Suit suit)
    {
        this.suit = suit;
        this.rank = rank;
    }
    // initializes deck
    public void initDeck()
    {
        for (Suit suit : Suit.values())
        {
            for (Rank rank : Rank.values())
            {
                deck.add(new Card(rank, suit));
            }
        }
    }
    // returns a copy of the deck    
    public static ArrayList<Card> newDeck()
    {
        return new ArrayList<Card>(deck);
    }

    public Rank getRank()
    {
        return rank;
    }

    public Suit getSuit()
    {
        return suit;
    }

    public String toString()
    {
        return rank +" of "+ suit;
    }

    public static void main(String[] args)
    {
        System.out.println(deck.toString());
    }

}

Your problem is that you never actually invoke initDeck, so the deck remains empty, as it was when the static initializer ran:

private static final List<Card> deck = new ArrayList<Card>();

Other problems:

1. initDeck() is an instance method, but deck is a static reference.
2. initDeck() is a method on Card.
3. deck is a static member of Card, but a card does not own or define a deck.
4. newDeck is nonsensical in the face of a static final deck.
5. Cards should not be delivering decks anyway.

In short, your design is messed up - you need to think more and harder about the entities and their inter-relationships.

It's simple, in your main method, you're just toString() an empty ArrayList. You haven't called initDeck() method in your main method at all.

When you ran your program private static final List<Card> deck = new ArrayList<Card>(); , deck was assigned an empty ArrayList.

it is very suspicious that your deck is private static final and your init method public and non-static. It can be initialized several times and contain more cards then you would expect. You may want to do the initialization in static block instead.

I would replace the code as follows:

1. make the deck public static final and unmodifiable (via Collections)
2. copy the body of your init method in static initializer like this:

static {
  for (Suit suit : Suit.values()) {
    for (Rank rank : Rank.values()) {
      deck.add(new Card(rank, suit));
    }
  }
}

1. delete initDeck completely

It's because initDeck() isn't called anywhere. Try to replace public void initDeck() with static.

The keyword final in you List<card> definition is for object that will have an starting value that cannot be changed.

Check it here