java - 在 Java 中从另一个类调用 ArrayList 和方法很困难

Question

第一次发帖，长期潜伏者。

我是一名计算机科学专业二年级学生，正在尝试编写二十一点游戏代码。这不是家庭作业，只是一个有趣的项目。由于尚未完成，因此游戏本身尚未准备好，因此请忽略该部分。我花了大约两个小时寻找答案，但无法将其他用户的类似问题与我自己的问题进行比较，因此我决定发布我的问题。

我的问题是“甲板”ArrayList。从我的 Blackjack.java 文件中，无论我做什么，我都无法调用它，我无法调用 Card 类中的任何方法，我无法操作它，我似乎无法在不收到某种错误的情况下执行任何操作。

public class Blackjack {
    public int bet;
    public int earnings = 0;
    public int total = 100;
    public boolean inputNeeded = true;

    public Blackjack() {
        Scanner s = new Scanner(System.in);

        System.out.println("               Welcome to Blackjack.");
        System.out.println("             Enter any key to continue.");
        System.out.println("         Otherwise, please type Exit to quit.");

        while (!s.nextLine().toString().toLowerCase().equals("exit")) //Main Game Loop - Only ends when user types Exit.
        {
            while (inputNeeded) {
                System.out.println("You currently have $" + total + ".");
                System.out.print("Please place your bets now. (Min $10): $");

                if (s.hasNextInt()) {
                    bet = s.nextInt();
                    String betString = String.valueOf(bet);
                    inputNeeded = false;

                    if (bet < 10 || bet % 5 != 0) {
                        System.out.println("Your bet is not valid. Your bet must be a minimum of $10 and be a factor of 5.");
                        System.out.println("");
                        inputNeeded = true;
                    }
                } else {
                    System.out.println("Your bet is not valid. Your bet must be a minimum of $10 and be a factor of 5.");
                    System.out.println("");
                }
            }
            inputNeeded = true; 

            /*
             * RESERVED SPACE (stuff to-do)
             * 
             * Deal two cards to dealer and player.
             * Flip cards, add totals
             * If dealer has ace, prompt user if he wants insurance incase dealer blacjack
             * Main loop, as long as neither player has blackjack, prompt user to hit, stay, double down etc.
             * Once loop exits, calculate bets, add into totals. 
             * Increase count of how many games it's been, shuffle the decks at X games depending on howManyDecks (card.java)
             * 
             * RESERVED SPACE (stuff to-do)
             * 
             */
            deck.shuffle();

            break; //until game is finished
        }

        System.out.print("Thank you for playing!");
    }

    public static void main(String[] args) {
        Blackjack game = new Blackjack();
    }
}

还有卡片类(我知道我可以循环完成 52 张卡片，但为了简单起见，我决定不这样做)。据我所知，如果我不想创建静态方法，我就必须创建“getter”方法。我不太确定返回方法将如何帮助我，例如，从 blackjack 类中洗牌，或者从 blackjack 类中抽牌(尚未实现)，因为这些方法将 void 作为其返回类型。我什至不确定我的 getter 方法是否正确，因为我以前从未尝试过“获取”构造函数所需的参数。

public class Card
    extends Blackjack //Do I need to extend this? <---- not sure
{
    public String name;
    public int value;
    public String suit;
    public int howManyDecks = 8; //most casino's use 8 decks for blackjack

    public Card(String n, int v, String s) {
        name = n;
        value = v;
        suit = s;

        ArrayList<Card> discard = new ArrayList<Card>(); //this will be for any card that is not currently in the deck, I could have called it 'temp'
        ArrayList<Card> deck = new ArrayList<Card>(howManyDecks * 52);

        for (int i = 0; i < howManyDecks; i++) {
            deck.add(new Card("Ace", 1, "Hearts"));
            deck.add(new Card("2", 2, "Hearts"));
            deck.add(new Card("3", 3, "Hearts"));
            deck.add(new Card("4", 4, "Hearts"));
            deck.add(new Card("5", 5, "Hearts"));
            deck.add(new Card("6", 6, "Hearts"));
            deck.add(new Card("7", 7, "Hearts"));
            deck.add(new Card("8", 8, "Hearts"));
            deck.add(new Card("9", 9, "Hearts"));
            deck.add(new Card("10", 10, "Hearts"));
            deck.add(new Card("Jack", 10, "Hearts"));
            deck.add(new Card("Queen", 10, "Hearts"));
            deck.add(new Card("King", 10, "Hearts"));
            deck.add(new Card("Ace", 1, "Spades"));
            deck.add(new Card("2", 2, "Spades"));
            deck.add(new Card("3", 3, "Spades"));
            deck.add(new Card("4", 4, "Spades"));
            deck.add(new Card("5", 5, "Spades"));
            deck.add(new Card("6", 6, "Spades"));
            deck.add(new Card("7", 7, "Spades"));
            deck.add(new Card("8", 8, "Spades"));
            deck.add(new Card("9", 9, "Spades"));
            deck.add(new Card("10", 10, "Spades"));
            deck.add(new Card("Jack", 10, "Spades"));
            deck.add(new Card("Queen", 10, "Spades"));
            deck.add(new Card("King", 10, "Spades"));
            deck.add(new Card("Ace", 1, "Diamonds"));
            deck.add(new Card("2", 2, "Diamonds"));
            deck.add(new Card("3", 3, "Diamonds"));
            deck.add(new Card("4", 4, "Diamonds"));
            deck.add(new Card("5", 5, "Diamonds"));
            deck.add(new Card("6", 6, "Diamonds"));
            deck.add(new Card("7", 7, "Diamonds"));
            deck.add(new Card("8", 8, "Diamonds"));
            deck.add(new Card("9", 9, "Diamonds"));
            deck.add(new Card("10", 10, "Diamonds"));
            deck.add(new Card("Jack", 10, "Diamonds"));
            deck.add(new Card("Queen", 10, "Diamonds"));
            deck.add(new Card("King", 10, "Diamonds"));
            deck.add(new Card("Ace", 1, "Clubs"));
            deck.add(new Card("2", 2, "Clubs"));
            deck.add(new Card("3", 3, "Clubs"));
            deck.add(new Card("4", 4, "Clubs"));
            deck.add(new Card("5", 5, "Clubs"));
            deck.add(new Card("6", 6, "Clubs"));
            deck.add(new Card("7", 7, "Clubs"));
            deck.add(new Card("8", 8, "Clubs"));
            deck.add(new Card("9", 9, "Clubs"));
            deck.add(new Card("10", 10, "Clubs"));
            deck.add(new Card("Jack", 10, "Clubs"));
            deck.add(new Card("Queen", 10, "Clubs"));
            deck.add(new Card("King", 10, "Clubs"));
        }
    }

    public void shuffle() {
        ArrayList<Card> temp = new ArrayList<Card>();
        while (!deck.isEmpty()) {
            int loc = (int) (Math.random() * deck.size());
            temp.add(deck.get(loc));
            deck.remove(loc);
        }
        deck = temp;
    }

    public Card getDeck() {
        return deck;
    }

    public Sting getCardName(int arrayIndex) {
        return deck(arrayIndex, Name);
    }

    public int getCardValue(int arrayIndex) {
        return deck(arrayIndex, Value);
    }

    public String getCardSuit(arrayIndex, Suit);
    {
        return deck(arrayIndex, Suit);
    }
}

尝试运行:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    deck cannot be resolved

    at Blackjack.<init>(Blackjack.java:61)
    at Blackjack.main(Blackjack.java:72)

感谢您提前提供的所有帮助!

Answer 1

问题很多...

• 您正在尝试运行无法编译的代码——切勿这样做。在尝试运行程序之前先解决编译问题。
• 您正尝试调用类中尚未声明的变量的方法。 Blackjack 需要一个牌组变量，如果您要调用它的方法，该变量就会被初始化。
• 我会考虑创建一个 Deck 类来保存 ArrayList 并具有一副牌的所有行为(方法)。
• Card 类不应该有套牌字段。从逻辑上讲，为什么一张卡牌需要知道它所在的牌组。
• 卡牌绝对不应该延长二十一点
• 相反，Card 应该封装单张卡牌的概念，即它的花色和等级，仅此而已。
• 如果需要，稍后您可以使用 HashMap 将每个卡片与图像或 ImageIcon 相关联。
• Card/Deck 概念是教授枚举时使用的规范示例之一，因此借用这个想法 - 将您的 Suit 和 Rank 放入枚举中，并让您的 Card 类保存每个枚举的字段。<

<小时/>

关于，

What do you mean by trying to run uncompilable code?

每当你看到这个:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    deck cannot be resolved

这恰恰意味着:您正在尝试运行无法编译的代码。您必须在编译阶段修复此问题，而不是在运行阶段。

I mean, without the deck.shuffle(); , it does compile and runs okay.

那么您必须在重新尝试运行代码之前修复 deck.shuffle() 错误。

Is it that the way this code is structured, trying to accomplish my goals will be impossible?

我会从头开始，使用更干净的类，尤其是 Card 类，它是一切的关键。像我建议的那样使用枚举，在这里阅读它们:Java enums tutorial .

"Blackjack needs a deck variable that is initialized if you're ging to call a method on it.", but I thought I could just use the Deck variable in the other class?

您只能对调用代码范围内的字段调用方法。这是一个基本的 Java 101 概念，因此您最好回顾一下如何调用类上的方法。您的 Blackjack 类没有牌组字段，它根本不存在于该类中，因此您无法对不存在的字段或变量调用方法。

Can't I reference arrays, objects, variables, static things, whatever you want etc from other classes one way or another? Sorry for my lack of understanding, I'm still very much a leaner.

这些是超出本站点范围的基本问题，建议您重新查看一本像样的 Java 书籍或教程的介绍性章节，从中受益。相信我，你不会后悔这样做的。