Question

在我的垄断游戏中，我在课堂上遇到了问题。我想知道玩家拥有多少次发货，从而确定租金。（这是游戏的丹麦版本，所以我认为规则因国家而异）。我使用Collections.frequency但由于某种原因它总是转到else语句并给我8倍的租金。这是代码：

package fields;

import java.util.Collections;
import java.util.Scanner;

public class Shipping extends Ownable
{
    public int rent;
    private int occurence;
    private String yesOrNo;
    private Shipping shipping;
    Scanner scan = new Scanner(System.in);

public Shipping(int fieldNumber, String fieldName, int price)
{
    super(fieldNumber, fieldName, price);
    this.rent = 500;
}

public int getRent()
{
    return rent;
}

@Override
public int getPrice()
{
    return price;
}

@Override
public String getName()
{
    return fieldName;
}

@Override
public int getNumber()
{
    return fieldNumber;
}

@Override
public matador.Player getOwner()
{
    return owner;
}

@Override
public void getConsequence()
{
    if(getOwner() == null)
    {
        System.out.println("Do you want to buy it? (Y/N)");
        yesOrNo = scan.next();

        if(yesOrNo.equalsIgnoreCase("y"))
        {
            matador.Main.currentPlayer.money -= getPrice();
            owner = matador.Main.currentPlayer;
            matador.Main.currentPlayer.ownedGrounds.add((Shipping) data.board[matador.Main.currentPlayer.getPosition()]);
            System.out.println(matador.Main.currentPlayer.getName()
                    + " bought " + getName());
        }
        else
        {
            System.out.println(matador.Main.currentPlayer.getName() +
                    " did not buy " + data.board[matador.Main.currentPlayer.getPosition()].getName());
        }
    }
    else if(getOwner() != matador.Main.currentPlayer)
    {
        occurence = Collections.frequency(owner.ownedGrounds, shipping);
        if(occurence == 1)
        {
            System.out.println(matador.Main.currentPlayer.getName() + " needs to pay " +
                    owner.getName() + " " + getRent());
            matador.Main.currentPlayer.money -= getRent();
            owner.money += getRent();
        }
        else if(occurence == 2)
        {
            System.out.println(matador.Main.currentPlayer.getName() + " needs to pay " +
                    owner.getName() + " " + (2 * getRent()));
            matador.Main.currentPlayer.money -= (2 * getRent());
            owner.money += (2 * getRent());
        }
        else if(occurence == 3)
        {
            System.out.println(matador.Main.currentPlayer.getName() + " needs to pay " +
                    owner.getName() + " " + (4 * getRent()));
            matador.Main.currentPlayer.money -= (4 * getRent());
            owner.money += (4 * getRent());
        }
        else
        {
            System.out.println(matador.Main.currentPlayer.getName() + " needs to pay " +
                    owner.getName() + " " + (8 * getRent()));
            matador.Main.currentPlayer.money -= (8 * getRent());
            owner.money += (8 * getRent());
        }
    }
}
}

我认为问题是我试图获得频率的对象，但我不知道。

提前感谢！

问候！

Answer 1

occurence = Collections.frequency(owner.ownedGrounds, shipping);

Collections.frequency依赖于对象的equals方法来将Collection中的对象与您希望找到的对象进行比较。由于您的Shipping课程似乎无法覆盖equals，因此使用Object的默认实施方式来比较参考资料。

因此，您将始终获得0的频率（除非您传递Shipping中已有的Collection引用，在这种情况下，您将获得{{1}的频率但是它可能仍然是错误的结果。）

Answer 2

Collections.frequency(c, o)使用equals（）方法进行比较。我可以看到你没有用你自己的实现覆盖它，因此它将默认使用引用的Object.equals（）。

虽然这个问题不是严格要求的should also implement .hashCode() when implementing equals()。

这是在javadoc中声明的那种。

返回指定集合中等于的元素数指定的对象。更正式地说，返回元素的数量e 在集合中（o == null？e == null：o.equals（e））。

垄断游戏问题

2 个答案: