Java的货币面额四舍五入问题

Question

所以我被分配到写一个程序，提示用户，并为双读取输入的数值（最大输入为[99.99] 99美元，99美分），我的编程类，这将代表一笔金额。我然后确定最少数量的各钞票和硬币来代表所述量所需的（10美元的钞票是所需的最大尺寸）。

我遇到四舍五入的问题。例如，输入99.99将返回3便士，当它应该是4便士。我明确我的老师告诉无法超越课堂上的材料（仅限于已就不见了，创建扫描仪，转换数据类型，以及铸造。这意味着没有任何的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

你会好起来的转换数字为整数（硬币的量）和计算基础上，作为这样就可以避免浮点错误，你现在正在经历的类型（它们是造成由浮点数表示为二进制）。

如果通过使用this步骤（您需要硬编码输入使用它），你可以看到错误。

的变化量作为设置由于98.99999999999949 20行四舍五入，所以这就是为什么一分钱去失踪