Question

我正在上高中的编程班，我被分配了一个基本的小计和顶级计算器，但我在一家餐馆工作，所以制作一个只让它的计算器似乎有点无意义你在一份食物中读到所以我试图让它能够接收多种食物并将它们添加到一个价格变量中。很抱歉，如果某些代码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，它会询问是否有用户想添加的其他食品，当我输入“是”或“否”时，该程序什么都不做。继续运行，但没有进一步。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"));

一旦您输入Yes，它就会一直坐在那里，什么都不做，因为done的值是Yes而且永远不会改变。

你的循环结构也有点奇怪。您的外部for循环运行的次数与第一个项目的数量相同。但是，你不应该只将这个数字乘以成本吗？因为您要么在用户输入的项目数量之前运行循环（通过事先询问它们），要么您没有问他们项目的总数，如果他们只是要求他们输入Yes想要添加更多物品;你不能真的做到这两点。

你的循环应该看起来像这样：

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();
}

Answer 2

当用户输入yes时你需要退出循环，所以你可以在这里使用label，如下所示：

  outerloop:
  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")){
                     break outerloop;
               }
            }

如果您未输入yes，则当前代码在while循环内不会执行任何操作。如果输入yes，由于你的while循环，它将陷入无限循环。这不是循环的效果方式，但是这段代码在当前代码中的变化最小。

Answer 3

你是while循环什么也没做，你已经给它一个条件，但它没有指令。

尝试这样的事情......（抱歉我生锈的java）

'public static void main(String[] args) {

//variable declaration
bool running = true

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;

while(running = true){
    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();

        if(done.equalsIgnoreCase("No")){
            running = false
        //Allows you to break out of the while loop if the user does not want to add anything else
        //DO NOT USE BREAK STATMENTS, IT IS A POOR PROGRAMMING PRACTICE.
        };//end if
    }//end for
}//end while

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

    //You should comment whats going on here
    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();

    //Output
    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));

}//end main

写循环/ while循环？

3 个答案: