Deck of Card

Design the data structure for a generic deck of cards. How you would subclass it to implement particular card games?

Think

Card has suit and value; Suit has four kinds with Club, Spade, Heart and Diamond.

About Enum Type

1. enum 类型不支持 public 和 protected 修饰符的构造方法，因此构造函数一定要是 private 或 friendly 的。也正因为如此，所以枚举对象是无法在程序中通过直接调用其构造方法来初始化的。
2. 定义 enum 类型时候，如果是简单类型 (No more constructor)，那么最后一个枚举值后不用跟任何一个符号；但如果有定制方法，那么最后一个枚举值与后面代码要用分号';'隔开，不能用逗号或空格。
3. 由于 enum 类型的值实际上是通过运行期构造出对象来表示的，所以在 cluster 环境下，每个虚拟机都会构造出一个同义的枚举对象。因而在做比较操作时候就需要注意，如果直接通过使用等号 ( ‘ == ’ ) 操作符，这些看似一样的枚举值一定不相等，因为这不是同一个对象实例。

Solution

class Card {
    // Define the Suit by Enum type
    public enum Suit {
        CLUBS(1), SPADE(2), HEART(3), DIAMOND(4);
        int value;
        private Suit(int val) {
            this.value = val;
        }
    }

    // Card has suit and value, only two kind of data need to store
    int val;
    Suit suit;


    public Card(int value, Suit suit) {
        this.val = value;
        this.suit = suit;
    }

    public int getVal(){
        return this.val;
    }

    public Suit getSuit(){
        return this.suit;
    }
}

BlackJack

• Face cards (kings, queens, and jacks) are counted as ten points.
• Ace can be counted as 1 point or 11 points
• Other cards with value less than ten should be counted as what it values.

class BlackJack extends Card{
    public BlackJack(int val, Suit suit) {
        super(val, suit);
    }

    @Override
    public int getVal(){
        int value = super.getVal();
        if(value < 10)
            return value；
        else if(value == 1)
            return 11;
        return 10;
    }

    public boolean isAce(){
        return super.getVal() == 1;
    }
}