等于方法覆盖会弄乱其他代码/更改输出吗？

Question

我正在为学校项目制作纸牌游戏。我需要我的 equals 方法能够正确地告诉我一张卡是否与另一张卡具有相同的等级。但是，我注意到只要等于重写存在，即使我不对任何东西使用“.equals()”，它似乎也会搞砸其他代码的输出。这是我的输出示例，其中 equals 方法处于活动状态：

Player 1
Has spoon? false
Is dealer? true
Hand: [7 of Clubs, 2 of Clubs, 8 of Spades, 8 of Clubs]
Dealer: 
Your dealer has a deck of 48 cards: 

Cards currently in deck: 3 of Hearts, 4 of Hearts, 5 of Hearts, 6 of Hearts, 9 of Hearts, 10 of Hearts, Jack of Hearts, Queen of Hearts, King of Hearts, Ace of Hearts, 2 of Spades, 3 of Spades, 4 of Spades, 5 of Spades, 6 of Spades, 7 of Spades, 9 of Spades, 10 of Spades, Jack of Spades, Queen of Spades, King of Spades, Ace of Spades, 2 of Clubs, 3 of Clubs, 4 of Clubs, 5 of Clubs, 6 of Clubs, 7 of Clubs, 8 of Clubs, 9 of Clubs, 10 of Clubs, Jack of Clubs, Queen of Clubs, King of Clubs, Ace of Clubs, 2 of Diamonds, 3 of Diamonds, 4 of Diamonds, 5 of Diamonds, 6 of Diamonds, 7 of Diamonds, 8 of Diamonds, 9 of Diamonds, 10 of Diamonds, Jack of Diamonds, Queen of Diamonds, King of Diamonds, Ace of Diamonds

我可以创建多个玩家并给他们每人发一定数量的牌。

在某些情况下，玩家会收到重复的牌，这是一个明显的问题。最重要的是，它不会从牌组中移除正确的牌，有时会移除正确的等级但移除错误的花色。请注意，该玩家手中的一些牌仍在牌组中，但取出了几张红心牌。

这是注释掉 equals 方法的输出，没有其他改变：

Player 1
Has spoon? false
Is dealer? true
Hand: [7 of Diamonds, Queen of Hearts, 6 of Diamonds, King of Spades]
Dealer: 
Your dealer has a deck of 48 cards: 

Cards currently in deck: 2 of Hearts, 3 of Hearts, 4 of Hearts, 5 of Hearts, 6 of Hearts, 7 of Hearts, 8 of Hearts, 9 of Hearts, 10 of Hearts, Jack of Hearts, King of Hearts, Ace of Hearts, 2 of Spades, 3 of Spades, 4 of Spades, 5 of Spades, 6 of Spades, 7 of Spades, 8 of Spades, 9 of Spades, 10 of Spades, Jack of Spades, Queen of Spades, Ace of Spades, 2 of Clubs, 3 of Clubs, 4 of Clubs, 5 of Clubs, 6 of Clubs, 7 of Clubs, 8 of Clubs, 9 of Clubs, 10 of Clubs, Jack of Clubs, Queen of Clubs, King of Clubs, Ace of Clubs, 2 of Diamonds, 3 of Diamonds, 4 of Diamonds, 5 of Diamonds, 8 of Diamonds, 9 of Diamonds, 10 of Diamonds, Jack of Diamonds, Queen of Diamonds, King of Diamonds, Ace of Diamonds, 

我相信这会完美无缺。玩家获得他们的特定卡牌，这些卡牌将从牌组中移除。

这是我的等于方法：

public boolean equals(Object obj) {
        if (!(obj instanceof Card)){
            return false;
        } else {
            Card card = (Card) obj;
            return card.cardNum == this.cardNum;
        }
    }

我猜这一定是在卡片从牌组中移除时发生的，而不是在它们被创建时发生的，因为即使使用 equals 方法，牌组仍然由 52 个单独的独特卡片对象组成。

所以，我使用 2 种方法从一副牌中取出一张牌：deal 和 deals

    /**
     * @return randomCard, the randomly selected card
     */
    public Card deal() {
        Random rand = new Random();
        Card randomCard;

        randomCard = m_cards.get(rand.nextInt(m_cards.size()));
        m_cards.remove(randomCard);

        return randomCard;
    }

    /**
     * @param n, the number of times deal is called
     * @return cardsDealt, a LinkedList containing the cards removed from the Deck.
     */
    public LinkedList<Card> deals(int n) {
        LinkedList<Card> cardsDealt = new LinkedList<Card>();

        for(int i = 0; i < n; i++) {
            cardsDealt.add(m_deck.deal());
        }
        // System.out.print("\nRemoving: ");
        return cardsDealt;
    }

这是我现在拥有的 Player 类代码：

import java.util.LinkedList;
public class Player {
    private int playerNum;
    private boolean hasSpoon;
    private boolean isDealer;

    static Dealer dealer = new Dealer();
    LinkedList<Card> hand;

    public Player(int playerNum) {
        this.playerNum = playerNum;
        this.hasSpoon = false;
        if(this.playerNum == 1) {
            this.isDealer = true;
        }
        this.hand = new LinkedList<Card>(dealer.deals(4));
    }

    public String toString() {
        return "\nPlayer " + playerNum + 
               "\nHas spoon? " + hasSpoon + 
               "\nIs dealer? " + isDealer + 
               "\nHand: " + hand
              + "\nDealer: " + dealer;
    }

    public static void main(String[] args) {
        Player player1 = new Player(1);

        System.out.println(player1);
    }
}

同样，这是针对学校的，所以不要直接给我答案，但我很想知道为什么会这样，并指出正确的方向。

Answer 1

public Card deal() {
    Random rand = new Random();
    Card randomCard;

    randomCard = m_cards.get(rand.nextInt(m_cards.size()));
    m_cards.remove(randomCard);

    return randomCard;
}

m_cards.remove(randomCard) – 想想这个方法如何知道要从集合中删除哪张卡片？准确的说，它调用equals 参数和集合中的每一项！

此方法的规范实现是（或多或少）：

public boolean remove(Object o) {
    Iterator<E> it = iterator();
    while (it.hasNext()) {
        if (Objects.equals(o, it.next())) {
            it.remove();
            return true;
        }
    }
    return false;
}

PS Random 实例应该被缓存，而不是在你每次需要它们的时候用new重新创建。如果这样做，您将无法获得良好的随机值，甚至可能连续多次得到相同的数字。