java - 通过/返回不起作用

Question

public class BlackJack {

    static String[] deck = new String[52];

    //Creates Deck of cards
    public static void main (String[] args)  {      
        String[] suit = { "Clubs", "Diamonds", "Hearts", "Spades" };
        String[] rank = { "2", "3", "4", "5", "6", "7", "8", "9", "10",
                "Jack", "Queen", "King", "Ace" };

        for (int a=0; a < rank.length; a++) {
            for (int b=0; b < suit.length; b++){
                deck[suit.length*a + b] = (rank[a] +" of "+ suit[b]);
            }
        }

        //Trying to get this to print out the returned card name
        String card = "G";
        randomCard(card);
        System.out.println(card);
    }

    //Pulls a random card from the deck
    public static String randomCard(String cardName) {          
        //Generates a random number between 0 and 52
        int card = (int)(Math.random()*53);
        cardName = (deck[card]);
        return cardName;

    }

}

所以我的 main 方法的第一部分生成了一副纸牌并且工作得很好(我已经单独测试过)。我正在尝试让我的第二种方法 randomCard 从牌组中返回一张随机抽取的牌。我只能让它打印出“G”，我可以测试它是否正常工作。帮助将不胜感激。谢谢!

Answer 1

您需要对返回值进行赋值。

card = randomCard(card);

在方法 cardName = deck[card]; 内部进行的赋值仅更新方法本地 String 引用 cardName 并且在外部没有任何影响方法的范围。

另请参阅 Collections.shuffle() 以更好的方式随机分发卡片。 .阅读this blog entry和 this one有关洗牌的更多信息。

ArrayList<String> deck = new ArrayList<String>();

String[] suit = { "Clubs", "Diamonds", "Hearts", "Spades" };
String[] rank = { "2", "3", "4", "5", "6", "7", "8", "9", "10",
        "Jack", "Queen", "King", "Ace" };

for (int a=0; a < rank.length; a++) {
    for (int b=0; b < suit.length; b++){
        deck.add(rank[a] +" of "+ suit[b]);
    }
}

Collections.shuffle(deck, new SecureRandom());
String randomCard = deck.get(0);