Equals method for PlayingCard Class, how to get working?

Question

I have been working on a PlayingCard class, and I am having difficulty writing an equals() method for the class. The intent for the equals method is to compare two playing cards to see if they are identical or not.

I have used an example from the Big Java Late Objects Book and altered it to try and check to see if the two cards are identical or not, but in both cases (identical and not identical), I get the same output. What is going wrong and how can I get it to work?

This is the PlayingCard class, with the equals method at the bottom.

public class PlayingCard
{

private Rank rank;
private Suit suit;

public PlayingCard(Rank rank, Suit suit)
{
    this.rank = rank;
    this.suit = suit;
}

public Rank getRank()
{   
    System.out.println(rank);
    return rank;
}

public Suit getSuit()
{
    System.out.println(suit);
    return suit;
}

@Override
public String toString()
{
  return getClass().getName() + "[rank " + rank + "suit " + suit + "]"; 
}

public void format()
{
    System.out.format(rank + " OF " + suit);
    System.out.println("");
}

@Override
public boolean equals(Object otherObject)
{
    if (otherObject == null)
    {
        System.out.println("Match");
        return false;
    }
    if (getClass() != otherObject.getClass())
    {
        System.out.println("Match");
        return false;
    }

    System.out.println("No Match, True");
    PlayingCard other = (PlayingCard) otherObject;
    return suit.equals(other.suit) && rank == other.rank;
}

}

And this is the current tester:

public class PlayingCardTester 
{
public static void main(String[] args) 
{
    PlayingCard test = new PlayingCard(Rank.ACE, Suit.DIAMONDS);
    PlayingCard test2 = new PlayingCard(Rank.FIVE, Suit.CLUBS);
    PlayingCard test3 = new PlayingCard(Rank.ACE, Suit.DIAMONDS);
    test.getRank();
    test2.getRank();
    test.getSuit();
    test2.getSuit();
    test.toString();
    test.format();
    test2.toString();
    test2.format();
    test.equals(test2);
    test.equals(test3);
    System.out.println("");
}

}

Edit:

Enum Rank:

public enum Rank 
{
TWO(2), THREE(3), FOUR(4), FIVE(5), SIX(6), SEVEN(7), EIGHT(8), NINE(9), 
TEN(10), JACK(11), QUEEN(12), KING(13), ACE(14);

private int value;

private Rank(int value)
{
    this.value = value;
}

public int getValue()
{
    return value;
}
}

Enum Suit:

public enum Suit 
{
SPADES(-2), CLUBS(-1), HEARTS(0), DIAMONDS(1);

private int value;

private Suit(int value)
{
    this.value = value;
}

public int getValue()
{
    return value;
}
}

And the output I get from the tester:

run:
ACE   // getRank and getSuit print out the Rank and Suit respectivly for 
FIVE  // for the card specified and return it
DIAMONDS
CLUBS
ACE OF DIAMONDS // toString and format work together to get output of
FIVE OF CLUBS   // cards to show what they are
No Match, True  // This is from the equals method, both outputs are the
No Match, True  // same, first test-test2, second test-test3.

BUILD SUCCESSFUL (total time: 1 second)

What I am trying to do is to compare PlayingCard test with test2 and test3 to see if they are the same card or not, as in, having the same suit and rank or not, and printing out if they are equal or not.

Edit 2: Current equals method alteration, still just getting false as an output for both tests.

    @Override
public boolean equals(Object otherObject)
{
    boolean set = false;
    if (!(otherObject instanceof PlayingCard))
    {
        set = false;
    }

    if (otherObject == this)
    {
        set = true;
    }
    System.out.println(set);
    return set;
}

Answer 1

This is not doing quite what you may think:

if (getClass() != otherObject.getClass())

You are comparing Class object references here. Even if the Classes are of the same type, they may have different Class object references returned by their respective getClass() methods. Better yet, use the instanceof operator.

@Override
public boolean equals(Object otherObject)
{
    if (otherObject == null)
    {
        System.out.println("Match");
        return false;
    }
    if (otherObject instanceof PlayingCard)
    {
        PlayingCard other = (PlayingCard) otherObject;
        return suit.equals(other.suit) && rank == other.rank;
    }

    return false;
}

A good example I'd recommend looking at is the Java String equals() method. The implementation there is perfect. Follow it as a guideline:

public boolean equals(Object anObject) {
    if (this == anObject) {
        return true;
    }
    if (anObject instanceof String) {
        String anotherString = (String) anObject;
        int n = value.length;
        if (n == anotherString.value.length) {
            char v1[] = value;
            char v2[] = anotherString.value;
            int i = 0;
            while (n-- != 0) {
                if (v1[i] != v2[i])
                        return false;
                i++;
            }
            return true;
        }
    }
    return false;
}

Also, I'd recommend you remove the print statements unless you are only doing it for debug purposes. The equals() comparison should only be comparing, not doing anything else.

Answer 2

Your original equals method was implemented correctly. The outputs are the same because the equals method prints the same result regardless of what suit.equals(other.suit) && rank == other.rank evaluates to.

Edit: You could see that with a small change to the end of your equals() method:

PlayingCard other = (PlayingCard) otherObject;
boolean result = suit.equals(other.suit) && rank == other.rank;
System.out.println("No Match, " + result);
return result;

I recommend removing the print statements, and testing your code with a test framework like JUnit.

You should, of course, override hashCode() as well.

Answer 3

You can create your comparator for that type of objects. It will be something like this:

    public class ComparatorCard<T extends PlayingCard> implements Comparator<T> {

    @Override
    public int compare(T objectOne, T ObjectTwo) { 

        return objectOne.toString().compareTo(ObjectTwo.toString()); // Change what you need where
    }
}

With this class you can also save the PalyingCards by an order in some Java structure that use priorities.