Java 模数运算符无法正常工作

Question

这个问题已经有答案了:

Is floating point math broken? (33 个回答)

已关闭 4 年前。

我正在编写一个小程序，当我输入金额时，它会给出每种硬币类别(25美分、10美分等)的最大金额。模运算符未返回正确的值。例如，当我输入金额“1.64”时，它应该返回:25 美分:6，一角硬币:1，镍币:0，便士:4。但我的问题在于便士。它一直只返回 3 便士。任何意见将不胜感激!

import java.util.Scanner;

public class Main{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter amount: ");
        double amount = in.nextDouble();

        int quarters = (int)(amount / 0.25);
        System.out.println("Quarters: " + quarters);

        amount = (amount % 0.25);

        int dimes = (int)(amount / 0.1);
        System.out.println("Dimes: " + dimes);

        amount = (amount % 0.1);

        int nickels = (int)(amount / 0.05);
        System.out.println("Nickels: " + nickels);

        amount = (amount % 0.05);

        int pennies = (int)(amount / 0.01);
        System.out.println("Pennies: " + pennies);
    }
}

输入金额:1.64宿舍:6一毛钱:1镍:0便士:3

Answer 1

我建议您使用基本减法，而不是在每个步骤后通过模数重置amount。然后简单地乘以最后的剩余总数就可以得到几美分。例如，

int quarters = (int) (amount / 0.25);
System.out.println("Quarters: " + quarters);

amount -= (quarters * 0.25); // (remove quarters)

int dimes = (int) (amount / 0.1);
System.out.println("Dimes: " + dimes);

amount -= (dimes * 0.1); // (remove dimes)

int nickels = (int) (amount / 0.05);
System.out.println("Nickels: " + nickels);

amount -= (nickels * 0.05); // remove nickels, all that's left is pennies (in cents)
System.out.println("Pennies: " + Math.round(100 * amount));