Java 货币面额四舍五入问题

Question

所以我被指派为我的编程编写一个程序 class 提示用户并将输入的值读取为双精度值（最大输入为 [99.99] 九十九美元和九十九美分), 这将代表货币金额。然后我要确定代表所述金额所需的每张钞票和硬币的最少数量（10 美元钞票是所需的最大尺寸）。

我在四舍五入时遇到问题。例如，输入 99.99 将 return 3 便士，而它应该是 4 便士。我的老师明确告诉我不要超出 class 中涵盖的 material（只涉及创建扫描器、转换数据类型和转换。这意味着没有 BigDecimal）。任何帮助将不胜感激。

import java.util.Scanner;

public class MoneyConversion
{
     public static void main(String[] args)
     {
          //Set variables for input, dollars, and cents
          double inputAmount, change;
          int tens, fives, ones;
          int quarters, dimes, nickels, pennies;

          //Create scanner to setup for user input
          Scanner scan = new Scanner(System.in);

          //Scan user input and store into double
          System.out.print("Enter monetary amount: ");
          inputAmount = scan.nextDouble();

          //Extract demical or cent amount from dollar amount
          change = (inputAmount - (int) inputAmount) * 100;

          System.out.println("That's equivalent to:");

          //Extract and print denomination for ten-dollar bills
          tens = (int) inputAmount / 10;
          inputAmount = inputAmount % 10;
          System.out.println(tens + " ten dollar bills");

          //Extract and print denomination for five-dollar bills
          fives = (int) inputAmount / 5;
          inputAmount = inputAmount % 5;
          System.out.println(fives + " five dollar bills");

          //Extract and print denomination for one-dollar bills
          ones = (int) inputAmount;
          System.out.println(ones + " one dollar bills");

          //Extract and print denomination for quarters
          quarters = (int) change / 25;
          change = change % 25;
          System.out.println(quarters + " quarters");

          //Extract and print denomination for dimes
          dimes = (int) change / 10;
          change = change % 10;
          System.out.println(dimes + " dimes");

          //Extract and print denomination for nickels
          nickels = (int) change / 5;
          change = change % 5;
          System.out.println(nickels + " nickels");

          //Convert value for change to integer value and print for pennies
          pennies = (int) change;
          System.out.println(pennies + " pennies");

     }

}

Answer 1

您最好将数字转换为整数（便士的数量）并据此进行计算，因为这样您就可以避免现在遇到的浮点错误类型 （他们是由浮点数表示为二进制引起的).

如果您逐步使用 this（您需要对输入进行硬编码才能使用它），您会看到错误。

由于第 20 行四舍五入，零钱设置为98.99999999999949，因此少了一分钱

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