Generating a constructor

Question

My assignment asks to create a constructor that takes no input. The constructor initializes the two non-static attributes in order for them to represent a standard deck or cards. Note that this means that the array of Cards should be initialized with an array of 52 elements containing all 52 possible cards belonging to a standard deck. You must use at least 1 loop to accomplish this (that is, you cannot write 52 statements to assign all possible values).

Hint: If you create a String array of size 4 with all the possible suits value in it, you can easily use two nested loops to initialize the array of cards.

I started writing my code, but I have trouble understanding what they mean by the hint. I know I have to create a multi-dimensional array and loop through the elements, but can't figure how to create that multi-dimensional array.

Here is my code:

public class Deck {

  // Declare the private attributes

  private Card[] cards;
  private int numberOfCardsLeft;

  // Access the private fields via public methods

  // Generate a constructor

  public Deck() {

    this.cards = new Card[][];

    // Iterate through all the elements of the array

    for (int i = 0; i < 4; i++) {

      // Iterate through all the elements of the subarrays

      for (int j = 0; j < 13; j++) {

        // code missing
      }
    }
  }
}

Here is the Card class:

public class Card {

  // Declare the private attributes

  private int cardValue;
  private String cardSuit;


  // Access the private fields via public methods

  // Generate a constuctor

  public Card(int value, String suit) {

    this.cardValue = value;
    this.cardSuit = suit.toLowerCase();

    // Check if the input is a valid playing card

    if (!(this.cardValue >= 1 || this.cardValue <= 13) && (this.cardSuit.equals("spades") || this.cardSuit.equals("hearts") || this.cardSuit.equals("diamonds") || this.cardSuit.equals("clubs"))) {

      // Throw an IllegalArgumentException

      throw new IllegalArgumentException("This is not a valid playing card!");
    }
  }

  public int getValue() {

    return cardValue;
  }

  public String getSuit() {

    return cardSuit;
  }
}

Here is my getCards() method:

// A get() method that returns an array of Cards containing all the cards that are left in the deck

public Card[] getCards() {

  // Create a copy of the original array

  Card[] cardsLeft = new Card[cards.length];

  // Iterate through all the elements of the array

  for (int i = 0; i < cardsLeft.length; i++) {

    cardsLeft[i] = cards[i];
  }

  return cardsLeft;
}

`Card[][] cards = new Cards[4][13]`: 4 suits, 52 cards total — fantaghirocco, Mar 28 '19 at 16:52
Why a multidimensional array ? Could you share the code of `Card` (or at least the signature of it) ? Appart from the multi-dimensional, your approach is good. Just add the card to the array in the part you wrote `code misssing` — vincrichaud, Mar 28 '19 at 16:52
You can not initialize a one dimensional with a two dimensional array — Samuel Philipp, Mar 28 '19 at 16:57
@vincrichaud How do I obtain the multidimensional array then? — Elizabeth, Mar 28 '19 at 16:59
@SamuelPhilipp How do I obtain the multidimensional array that represents the card of the deck — Elizabeth, Mar 28 '19 at 17:00

Samuel Philipp · Accepted Answer · 2019-03-30T12:52:54.747

1

First of all you should an array of suits:

String[] suits = new String[]{"clubs", "hearts", "spades", "diamonds"};

To initialize a one dimensional array you can use the following code:

Card[] cards = new Card[52];
for (int i = 0; i < suits.length; i++) {
    for (int j = 0; j < 13; j++) {
        cards[i * 13 + j] = new Card(j + 1, suits[i]);
    }
}

If you need a two dimensional array use:

Card[][] cards = new Card[4][13];
for (int i = 0; i < suits.length; i++) {
    for (int j = 0; j < 13; j++) {
        cards[i][j] = new Card(j + 1, suits[i]);
    }
}

At the end the condition in your Card class is always false, because !(this.cardValue >= 1 || this.cardValue <= 13) is always false. I assume you are looking for something like this:

if (this.cardValue < 1 || this.cardValue > 13 ||
        !(this.cardSuit.equals("spades") || this.cardSuit.equals("hearts") ||
                this.cardSuit.equals("diamonds") || this.cardSuit.equals("clubs"))) {
    throw new IllegalArgumentException("This is not a valid playing card!");
}

Your getCards() method looks good and works as expected. Here some more options to copy an array:

Arrays.copyOf():

Card[] cardsCopy = Arrays.copyOf(cards, cards.length);

System.arraycopy():

Card[] cardsCopy = new Card[cards.length];
System.arraycopy(cards, 0, copy3, 0, cards.length);

Array.clone():

Card[] cardsCopy = cards.clone();

edited Mar 30 '19 at 12:52

answered Mar 28 '19 at 17:08

Samuel Philipp

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Wouldn't it be cards[i][j] = new Card (suits[i], j +1);? – Elizabeth Mar 28 '19 at 17:13
And isn't String[] suits = {"spades", "hearts", "diamonds", "clubs"}; equivalent to the first statement? – Elizabeth Mar 28 '19 at 17:16
1

Then the sub-array should be new Card[13][4] – Elizabeth Mar 28 '19 at 17:19
No, I mean we can discard the new String[] prior to naming the suits – Elizabeth Mar 28 '19 at 17:19
And the sub-array should be new Card[13][4] – Elizabeth Mar 28 '19 at 17:28
Thank you for your help! Sorry for all those questions I am quite new with Java – Elizabeth Mar 28 '19 at 17:33
Quick question, I also need to create a getCards() which takes no inputs and returns an array of Cards with all the cards that are left in the deck. But what do it mean when they say that no one should be able to use getCards() and, for instance, made this deck a trick deck. – Elizabeth Mar 28 '19 at 17:37

Generating a constructor

1 Answers1