难以从 Java 中的另一个 Class 调用 ArrayLists 和方法

Question

第一次 post呃，长期潜伏者。

我是计算机科学专业的二年级学生，正在尝试编写二十一点游戏代码。这不是家庭作业，它只是一个有趣的项目。这还没有完成，所以游戏本身还没有准备好，所以请忽略该部分。我花了大约两个小时在 SO 上搜索答案，但无法将其他用户的类似问题与我自己的问题进行比较，所以我决定 post 我的问题。

我的问题是 'deck' ArrayList。从我的 Blackjack.java 文件中，无论我做什么，我都无法调用它，我无法调用我的 Card class 中的任何方法，我无法操作它，我似乎无法在没有收到一些东西的情况下做任何事情某种错误。

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 ): $");

                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  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  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 class（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）。根据我的阅读，如果我不想制作静态方法，我必须制作 'getter' 方法。我不太确定 return 方法将如何帮助我，例如，从 blackjack class 洗牌，或从 blackjack class 抽牌（尚未实现），因为这些方法的 return 类型是 void 。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 'get' 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)

提前感谢大家的帮助！

Answer 1

很多问题...

您正在尝试运行不可编译的代码 -- 永远不要这样做。在尝试运行程序之前先解决编译问题。
您正在尝试对尚未在 class 中声明的变量调用方法。 Blackjack 需要一个 deck 变量，如果您要在其上调用方法，则该变量已初始化。
我会考虑创建一个 Deck class，它包含 ArrayList 并且具有一副纸牌的所有行为（方法）。
卡片 class 不应有牌组区域。从逻辑上讲，为什么卡片需要知道它所在的牌组。
Card 绝不能延长 Blackjack
相反，Card 应该封装单张 Card 的概念，意思是它的花色和等级，没有别的。
稍后您可以根据需要使用 HashMap 将每张卡片与图像或 ImageIcon 相关联。
Card/Deck 概念是教授枚举时使用的典型示例之一，所以借用这个想法——将你的 Suit 和 Rank 放入枚举中，并让你的 Card class 持有一个字段这些枚举中的每一个。

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.

然后您必须修复 deck.shuffle() 错误，然后再尝试运行代码。

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清洁的 classes，尤其是您的卡 class，这是一切的关键。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?

您只能在调用代码范围内的字段上调用方法。这是一个基本的 Java 101 概念，因此您最好回顾一下如何调用 classes 上的方法。您的 Blackjack class 没有甲板区域，它根本不存在于 class 中，因此您不能在不存在的区域或变量上调用方法。

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.

这些基本问题超出了本网站的范围，建议您重新复习一本不错的 Java 书籍或教程的介绍性章节，这会对您有所帮助。相信我，你不会后悔的。

难以从 Java 中的另一个 Class 调用 ArrayLists 和方法

Difficulty calling ArrayLists and Methods from another Class in Java

java

methods

getter

class

arraylist