Comparing rank in an enum

Question

I have the following enum which represents a CardRank

public enum CardRank
{
    DEUCE('2'), TREY('3'), FOUR('4'), FIVE('5'), SIX('6'), SEVEN('7'),
    EIGHT('8'), NINE('9'), TEN('T'), JACK('J'), QUEEN('Q'), KING('K'), 
    ACE('A');

    private char symbol;

    private CardRank(char symbol)
    {
        this.symbol = symbol;
    }

    public char getSymbol()
    {
        return this.symbol;
    }
}

The CardRank is represented in ascending order. I need to compare the ranks in order to know which rank is greater than the other. I can use > operator with the numerical values but not with the char values.

// this will print out TRUE for all numerical values compared 
// but FALSE for the chars
if (card.getRank().getSymbol() > anotherCard.getRank().getSymbol()) {
    System.out.println("true");
} else {
    System.out.println("false");
}

Any ideas?

Use a Comparator here. You can make it a static public inner class to the enum if you'd like. — Hovercraft Full Of Eels, May 19 '12 at 17:46
you may want to add a low ace to this if you are concerned with straights. — Ray Tayek, May 19 '12 at 17:55

JB Nizet · Accepted Answer · 2012-05-19T18:06:00.270

15

if (card.getRank().compareTo(anotherCard.getRank()) > 0)

is what you need.

You may alwo use the ordinal:

if (card.getRank().ordinal() > anotherCard.getRank().ordinal())

Enums have a natural ordering defined by their ordinal. And the ordinal of an enum is attributed based on its position in the declaration. So DEUCE has ordinal 0, TREY has ordinal 1, etc.

edited May 19 '12 at 18:06

answered May 19 '12 at 17:44

JB Nizet

678,734
91
1,224
1,255

I would avoid ordinals at all costs. It is considered bad form to use an enum ordinal in anything other then framework type code. [Ordinal Documentation](http://docs.oracle.com/javase/7/docs/api/java/lang/Enum.html#ordinal%28%29), [Can I specify ordinal for enum (java)](http://stackoverflow.com/questions/5372855/can-i-specify-ordinal-for-enum-java) – Zixradoom Apr 24 '14 at 14:22

score 1 · Answer 2 · answered May 19 '12 at 17:55

Consider using a Comparator for this. It can be a public static inner class if you desire:

import java.util.Comparator;

public enum CardRank implements Comparable<CardRank> {
   DEUCE('2'), TREY('3'), FOUR('4'), FIVE('5'), SIX('6'), SEVEN('7'), EIGHT('8'), NINE(
         '9'), TEN('T'), JACK('J'), QUEEN('Q'), KING('K'), ACE('A');

   private char symbol;
   private static CardRankComparator cardRankComparator = new CardRankComparator();

   private CardRank(char symbol) {
      this.symbol = symbol;
   }

   public char getSymbol() {
      return this.symbol;
   }

   public int compareRank(CardRank otherCardRank) {
      return cardRankComparator.compare(this, otherCardRank);
   }

   // public so that this can be used for sorting if need be
   public static class CardRankComparator implements Comparator<CardRank> {
      private static final String RANKS = "23456789TJQKA";

      @Override
      public int compare(CardRank cr1, CardRank cr2) {
         int rank1 = RANKS.indexOf(String.valueOf(cr1.getSymbol()));
         int rank2 = RANKS.indexOf(String.valueOf(cr2.getSymbol()));
         return rank1 - rank2;
      }
   }
}

This answer is overcomplicated. 1. Using a String to define an order means each time you call compare, you need to scan through the string. 2. Enums are by design comparable. — kamczak, Jun 15 '16 at 11:22

Comparing rank in an enum

2 Answers2