basic-computer-games/10_Blackjack/java/src/Card.java

/**
 * This is an example of an "record" class in Java. That's just a fancy way
 * of saying the properties (value and suit) can't change after the object has
 * been created (it has no 'setter' methods and the properties are implicitly 'final'). 
 *
 * Immutability often makes it easier to reason about code logic and avoid
 * certain classes of bugs.
 *
 * Since it would never make sense for a card to change in the middle of a game,
 * this is a good candidate for immutability.
 */
record Card(int value, Suit suit) {

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

	public Card {
        if(value < 1 || value > 13) {
            throw new IllegalArgumentException("Invalid card value " + value);
        }
        if(suit == null) {
            throw new IllegalArgumentException("Card suit must be non-null");
        }
	}

    public String toString() {
        StringBuilder result = new StringBuilder(2); 
        if(value == 1) {
            result.append("A");
        } else if(value < 11) {
            result.append(value);
        } else if(value == 11) {
            result.append('J');
        } else if(value == 12) {
            result.append('Q');
        } else if(value == 13) {
            result.append('K');
        }
        // Uncomment to include the suit in output. Useful for debugging, but
        // doesn't match the original BASIC behavior.
        // result.append(suit.name().charAt(0));
        return result.toString();
    }

    /**
     * Returns the value of {@link #toString()} preceded by either "AN " or "A " depending on which is gramatically correct.
     * 
     * @return "AN [x]" when [x] is "an" ace or "an" 8, and "A [X]" otherwise.
     */
    public String toProseString() {
		if(value == 1 || value == 8) {
            return "AN " + toString();
        } else {
            return "A " + toString();
        }
    }

}