Java Example Compare Poker Card Value

Compare Poker Card Value

Introduction

To demonstrate the power of object oriented programming, I write a Java program to compare the value of 2 poker cards, using inheritance.

For normal card, from small to large 2 3 4 ... 10 K Q K Ace, eg. 2 of diamond < 3 of diamond For big2 game, 2 is the biggest value, 3 is the smallest. 3 4 5 ... Q K A 2, eg. 2 of diamond > 3 of diamond

I do not create 2 different classes for normal card and big2 card, but inherited the big2 card from normal card (standard card). Many of the properties of the 2 classes are the same. New big2 card comparison can be created with little code added to the new class.

To simplify the program, I do not shuffle the cards, just use the first 2 cards for comparison. You can modified to compare 2 random cards.

class Card { … }, class CompareNormalCard use Card.

class BigTwoCard extends Card { … }, class CompareBigTwoCard use BigTwoCard.

Card.java

$ edit Card.java
class Card {
    private int id; // 0-51, id and value are the same for normal card
    protected int f, v; // f is diamond, club etc, v is 0-9TJKQA
    // use protected because the value was referred inside sub class

    Card() {} // constructor

    Card(int n) { this.setId(n); }

    void setId(int n) {
        this.id= n%52; // id not >= 52
        f= this.id/13; // pre-calculated for getValue(), to save time
        v= this.id%13;
    }

    int getId() { return this.id; }

    // value and id are the same for normal card    
        int getValue() {
        return this.id;
    }

    // return same value==0, this card smaller -1, this card bigger 1
    int isCompare(Card card) {
        if (this.getValue()>card.getValue())
            return 1;
        else if (this.getValue()<card.getValue())
            return -1;

        return 0;
    }

    // for display as D2 DJ DQ DK DA, C2 CJ ...
    // D2 is 2 of diamond
    String getString() {
        int f; // suit 0-Diamond, 1-Club, 2-Heart, 3-Spade
        int v; // 0-2, 1=3... 8=T 9=J 10=Q 11=K 12=A
        String pattern, number;

        f= id/13; // duplicate in setId(). f is protected, can be changed, but id is private
        v= id%13;

        switch(f) {
            case 0: pattern= "D"; break;
            case 1: pattern= "C"; break;
            case 2: pattern= "H"; break;
            case 3: pattern= "S"; break;
            default: pattern= "x";
        }

        if (v>=0 && v<8)
            number= "" + (v+2);
        else if (v==8)
            number= "T";
        else if (v==9)
            number= "J";
        else if (v==10)
            number= "Q";
        else if (v==11)
            number= "K";
        else if (v==12)
            number= "A";
        else
            number= "0";

        return pattern+number;
    }
}

CompareNormalCard.java

$ edit CompareNormalCard.java
public class CompareNormalCard {
    public static void main(String[] args) {
        Card card1= new Card(0),
        card2= new Card(1);
        String symbol;

        if (card1.isCompare(card2)>0)
            symbol= ">";
        else
            symbol= "<";

        System.out.println(card1.getString() + symbol +
            card2.getString());
    }
}

$ javac CompareNormalCard.java && java CompareNormalCard
==>D2<D3

Note: Diamond 2 is smaller than diamond 3

to be continue...CompareBigTwoCard.java