java - 定义类名 Money

Question

我坚持使用加/减方法来定义一个名为 Money 的类，该类的对象代表美元的金额。该类应该有 2 个 int 类型的实例变量，分别表示美元和美分的金额。包括一个具有 2 个 int 类型参数(表示美元和美分)的构造函数，一个具有 1 个 int 类型构造函数(表示金额为零的美元)和一个无参构造函数。包括用于加法和减法的方法 add 和 minus ，并返回 Money 类型的值。包括一组合理的访问器和修改器方法以及 equals 和 toString 方法。

再次，我陷入了加/减部分，只是无法确定它。另外，等于部分有点令人困惑。是的，这是家庭作业。我正在尽最大努力，但需要一点插入。

请看一下......

public class Money {

    private static  int dollars;
    private static int cents;

    public Money()
    {

    }

    public Money(int dollars, int cents)
    {
        this.dollars = dollars;
        this.cents = cents;
    }

    public Money(int dollars)
    {
        this.dollars = dollars;
    }



    public int getDollars() {
        return dollars;
    }

    public void setDollars(int dollars) {
        this.dollars = dollars;
    }

    public int getCents() {
        return cents;
    }

    public void setCents(int cents) {
        this.cents = cents;
    }


    public static Money add(Money m1, Money m2)
    {
        int cash = m1.dollars + m2.dollars;
        int change = m1.cents + m2.cents;
        return new Money(dollars, cents);


    }

    public static int MinusMoney(int m3, int m4)
    {
        return (m3-m4);
    }
    public boolean equals(double YourMoney)
    {
        boolean result;
        if (YourMoney > 0)
        {
            dollars += cents;
            result = true;
        }
        else
        {
            result = false;
        }
        return result;


    }

    public String toString()
    {
        return ("$" + getDollars() + "." + getCents());
    }

    public static void main(String[] args)
    {
        Money MyMoney = new Money(2,30);

        System.out.println("You have " + MyMoney.toString());

        Money MyMoney1 = new Money(2,30);
        Money MyMoney2 = new Money(3,10);

        System.out.println("You now have " + Money.add(MyMoney1, MyMoney2));

    }

}

Answer 1

要求规定对对象的操作(例如加法和减法)返回一个新实例而不是更改当前实例。因此:

class Money {
    private int dollars;
    private int cents;

    public Money(int dollars, int cents) {
        if (dollars < 0 || cents < 0)
            throw new IllegalArgumentException("Negative dollars or cents");
        this.dollars = dollars;
        this.cents = cents;
    }

    public Money add(Money other) {
        int cents = this.cents + other.cents;
        return new Money(this.dollars + other.dollars + cents / 100, cents % 100);
    }
}

对于equals，通常会定义它来覆盖Object.equals，这意味着它需要接受一个Object而不是一个双:

public boolean equals(Object other) {
    return other != null && other.getClass() == Money.class
        && this.dollars == (Money)other.dollars
        && this.cents == (Money)other.cents;
}