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;
}

Answer 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:

1. Arrays.copyOf():

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

2. System.arraycopy():

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

3. Array.clone():

Card[] cardsCopy = cards.clone();