动态计算找零到最接近的10美元

Question

我是Java新手，我正在尝试弄清楚如何动态地计算到最接近10美元的零头。例如，用户输入一个值(34.36)，然后我的代码就会计算账单的小费、税金和总金额(总计44.24)。如果没有用户输入，我需要从$50.00开始计算变化。我试图从44.24四舍五入到50.00，但没有运气，显然我做错了什么。我已经尝试了Math.round，并尝试使用%查找剩余部分。任何关于如何获得由于最近的10美元价值的总变化的帮助将是很大的。提前谢谢你，下面是我的代码: Full dis-closer，这是一个作业项目。

import java.util.Scanner; 
import java.text.NumberFormat;
import java.lang.Math.*;

public class test1
{
public static void main(String[] args)
{
    Scanner sc = new Scanner(System.in);
    //Get input from user
    System.out.println("Enter Bill Value:                   ");
    double x = sc.nextDouble();

    //Calculate the total bill
    double salesTax = .0875;
    double tipPercent = .2;
    double taxTotal = (x * salesTax);
    double tipTotal = (x * tipPercent);
    double totalWithTax = (x + taxTotal);
    double totalWithTaxAndTip = (x + taxTotal + tipTotal);

    //TODO:  Test Case 34.36...returns amount due to lower 10 number
    //This is where I am getting stuck                  
    double totalChange = (totalWithTaxAndTip % 10);




    //Format and display the results
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    NumberFormat percent = NumberFormat.getPercentInstance();

    //Build Message / screen output
    String message =
        "Bill Value:                         " + currency.format(x) + "\n" + 
        "Tax Total:                          " + currency.format(taxTotal) + "\n" +
        "Total with Tax:                     " + currency.format(totalWithTax) + "\n" +
        "20 Percent Tip:                     " + currency.format(tipTotal) + "\n" +
        "Total with Tax and 20 Percent Tip:  " + currency.format(totalWithTaxAndTip) + "\n" +
        "Total Change:                       " + currency.format(totalChange) + "\n";

    System.out.println(message);

}
}

Answer 1

你让double totalChange = round((totalWithTaxAndTip / 10)) * 10;

Answer 2

Math.ceil(double)将向上舍入一个数字。所以你需要的是这样的东西：

 double totalChange = (int) Math.ceil(totalWithTaxAndTip / 10) * 10;

对于totalWithTaxAndTip =44.24时，totalChange = 50.00

对于totalWithTaxAndTip = 40.00，totalChange = 40.00

Answer 3

Math.round将一个数字舍入为最接近的整数，因此，正如其他人所示，您需要除以10，然后在舍入后乘以10：

double totalChange = tenderedAmount - totalWithTaxAndTip;

double totalChangeRounded  = 10 * Math.round(totalChange / 10);