java - 带哨兵循环的 switch 语句

Question

我在使 sum 函数正常工作时遇到一些问题。我正在尝试创建一个程序，使用开关结构和哨兵循环来请求产品编号和数量。它将一直运行直到输入 0。它应该计算输入的产品总数和输入的所有产品的总值(value)。数量很好。这是仅适用于输入的第一个产品的总值(value)。在按下 0 之前，我无法获得继续添加的总和。任何帮助将不胜感激!!

import java.util.Scanner;

   public class Mailorder {

      public static void main(String[] args) {

    //create a scanner
    Scanner input = new Scanner(System.in);

    //declare variables

    double product1 = 3.75;
    double product2 = 5.95;
    double product3 = 8.75;
    double product4 = 6.92;
    double product5 = 8.75;
    double product6 = 7.87;
    double total = 0.00;

    //read in product # 
    System.out.print("Enter a product number: ");
        int product = input.nextInt();

    //read in quantity sold
    System.out.print("Enter quantity sold for 1 day: ");
        int quantity = input.nextInt();

    //switch case
    switch (product) 
      {
        case 1: total = product1 * quantity; break;
        case 2: total = product2 * quantity; break;
        case 3: total = product3 * quantity; break;
        case 4: total = product4 * quantity; break;
        case 5: total = product5 * quantity; break;
        case 6: total = product6 * quantity; break;
      default: System.out.println("ERROR: Invalid product number");
      }

    //keep reading data until the input is 0
    int sum1 = 0;
            while (quantity != 0) {
                     sum1 += quantity;

    int sum2 = 0;
            while (total != 0) {
                    sum2 +=total;
        }
     //read the next data
            System.out.print("Enter a product number: ");
                    product = input.nextInt();

            System.out.print("Enter quantity sold for 1 day: ");
                    quantity = input.nextInt();
    }

    //print results
    System.out.println("The total number of products sold last week " + sum1);
    System.out.println("The total retail value of all products sold last week " + sum2);

}
}

Answer 1

这里存在几个范围界定问题。

首先，您已将 switch 语句置于循环之外。您应该将其放在循环内。

其次，sum2 存在范围界定问题。它在哨兵循环内部声明，但在外部引用。我不确定为什么你有一个嵌套循环添加到 sum2 中。以下是解决这些问题的代码:

    public class Mailorder {

    public static void main(String[] args) {

        //create a scanner
        Scanner input = new Scanner(System.in);

        //declare variables

        double product1 = 3.75;
        double product2 = 5.95;
        double product3 = 8.75;
        double product4 = 6.92;
        double product5 = 8.75;
        double product6 = 7.87;

        //read in product #
        System.out.print("Enter a product number: ");
        int product = input.nextInt();

        //read in quantity sold
        System.out.print("Enter quantity sold for 1 day: ");
        int quantity = input.nextInt();


        //keep reading data until the input is 0
        int sum1 = 0;
        int sum2 = 0;
        while (quantity != 0) {
            sum1 += quantity;

            double total = 0.00;
            //switch case
            switch (product)
            {
                case 1: total += product1 * quantity; break;
                case 2: total += product2 * quantity; break;
                case 3: total += product3 * quantity; break;
                case 4: total += product4 * quantity; break;
                case 5: total += product5 * quantity; break;
                case 6: total += product6 * quantity; break;
                default: System.out.println("ERROR: Invalid product number");
            }
            sum2 += total;

            //read the next data
            System.out.print("Enter a product number: ");
            product = input.nextInt();

            System.out.print("Enter quantity sold for 1 day: ");
            quantity = input.nextInt();
        }


        //print results
        System.out.println("The total number of products sold last week " + sum1);
        System.out.println("The total retail value of all products sold last week " + sum2);

    }
}