java - 编写 for 循环/while 循环？

Question

我在高中的编程课上，我的作业是制作一个基本的小计和顶级计算器，但我在一家餐馆工作，所以制作一个只能让你在一种食物中读到。因此，我尝试让它能够接收多种食品并将它们添加到一个价格变量中。抱歉，如果某些代码可能看起来效率低下或冗余。当然这只是高中。

问题是，当我运行它时，它会询问用户是否想要添加其他食品，当我输入"is"或“否”时，程序什么也不做。继续奔跑，但不再前进。有什么解释吗？

import java.text.NumberFormat;
import java.util.Scanner;

public class Price {

    /**
     * @param args
     */
    public static void main(String[] args) {

        final double taxRate = .0887; //8.87% Tax Rate
        double tipRate;
        int quantity1;
        Scanner kb = new Scanner(System.in);
        double subtotal, tax, tip, totalCost1, unitPrice1 = 0;
        String done;

        System.out.println ("How many of the first item did you get?: ");
        quantity1 = kb.nextInt();

        for (int i = 0; i < quantity1; i++)
        {
        System.out.println ("What was the price of that single item "+(i+1) + ": ");
        unitPrice1 = kb.nextDouble();

        System.out.println ("Was there another food item you'd like to add?: ");
        done=kb.next();
        while (done.equalsIgnoreCase("Yes"));
        }

        System.out.println ("What percent would you like to tip? (Formatted like 0.10 for 10%, 0.20 for 20%, etc.): ");
        tipRate = kb.nextDouble();

        subtotal= quantity1 * unitPrice1;
        tax = subtotal * taxRate;
        totalCost1 = subtotal + tax;
        tip = totalCost1 * tipRate;
        totalCost1 = totalCost1 + tip;


        //Formatting
        NumberFormat money = NumberFormat.getCurrencyInstance();
        NumberFormat tipMoney = NumberFormat.getCurrencyInstance();
        NumberFormat taxPercent = NumberFormat.getPercentInstance();
        NumberFormat tipPercent = NumberFormat.getPercentInstance();


        System.out.println ("Your total before tax is: " + money.format(subtotal));
        System.out.println ("The tax is " + money.format(tax) + " at " + tipPercent.format(taxRate));
        System.out.println ("The tip at " + tipPercent.format(tipRate) + " is " + tipMoney.format(tip));

    }

}

Answer 1

这里有一个无限循环:

while (done.equalsIgnoreCase("Yes"));

输入 Yes 后，它会继续坐在那里什么都不做，因为 done 的值是 Yes并且永远不会改变。

而且你的循环结构有点奇怪。您的外for循环运行的次数与第一项的数量相同。但您不应该只将该数字乘以成本吗？因为您要么运行循环与用户输入的项目数一样长(通过预先询问他们)，要么您不询问他们项目总数，而只是要求他们输入 Yes如果他们想添加更多项目；你实际上无法两者兼得。

你的循环可能看起来像这样:

String input = "Yes";
while(input.equalsIgnoreCase("Yes")) {
    System.out.println ("How many of the first item did you get? ");
    quantity1 = kb.nextInt();

    System.out.println ("What was the price of that single item? ");
    unitPrice1 = kb.nextDouble();

    //total += unitPrice1 * quantity1 - you don't have this in your code, but this is where you would be calculating the running total

    System.out.println("Was there another food item you'd like to add? ");
    input = kb.next();
}