输入数量时中断while循环的问题

Question

我有一个问题。我基本上完成了我的程序，除了我创建的 while 循环的最后一个中断。如果我输入 -1 以跳出我的第一个输出问题“输入产品编号 (1-5) 或 -1 以退出”，它就会毫无问题地跳出。如果我在第二个问题“输入数量或 -1 退出”中输入 -1，它只会循环回到下一个产品编号请求。

我已尝试查找一些有关打破 while 循环的其他信息，并尝试将相同的逻辑应用于我现有的代码。不幸的是，我仍然遇到同样的问题。看起来这个特定的请求不是一个重复的问题，所以我觉得问它是安全的。我到底做错了什么，因为经过大约一个小时的努力想弄清楚这一点，我简直要发疯了。任何方向将不胜感激。

谢谢，

进步

导入 java.util.Scanner;

公共类 ModuleFour {

public static void main(String[] args) {

    int pNumber = 0; //declaring integer for Product Number
    int pQuantity= 0; //declaring integer quantity of Product
    double totalcost = 0; //declaring double for Total Cost of combined Product
    double cost = 0; //declaring double for cost of each Product
        Scanner productTotal = new Scanner(System.in); //create scanner productTotal
        pNumber = 0;
        pQuantity = 0;
    while (pNumber >= 0 && pNumber <=5) //set condition of pNumber for while loop
    {
        System.out.println("Enter Product Number (1-5) or -1 to Quit"); //print out asking for input
        pQuantity = productTotal.nextInt(); //
    switch(pQuantity) { //begin switch statement
    case 1: //start of cases, all are the same. 
        System.out.println("Product " + (pNumber+1));
        System.out.println("Enter Quantity or -1 to Quit");
        pQuantity = productTotal.nextInt(); 
        cost = 2.98; //declare cost of case 1. Same method for each case. 
        totalcost = totalcost + cost*pQuantity; //setting totalcost algorithm.
        System.out.println("Current total cost: " + totalcost); //print out the current totalcost.
        pNumber++; //increase value of pNumber by 1. Same for each case. 
    break; //break out of Case 1. Same for each case.
    case 2:
        System.out.println("Product " + (pNumber+1));
        System.out.println("Enter Quantity or -1 to Quit");
        pQuantity = productTotal.nextInt();
        cost = 4.50;
        totalcost = totalcost + cost*pQuantity;
        System.out.println("Current total cost: " + totalcost);
        pNumber++;
    break;
    case 3:

        System.out.println("Product " + (pNumber+1));
        System.out.println("Enter Quantity or -1 to Quit");
        pQuantity = productTotal.nextInt();
        cost = 9.98;
        totalcost = totalcost + cost*pQuantity;
        System.out.println("Current total cost: " + totalcost);
        pNumber++;
    break;
    case 4:
        System.out.println("Product " + (pNumber+1));
        System.out.println("Enter Quantity or -1 to Quit");
        pQuantity = productTotal.nextInt();
        cost = 4.49;
        totalcost = totalcost + cost*pQuantity;
        System.out.println("Current total cost: " + totalcost);
        pNumber++;
    break;
    case 5:
        System.out.println("Product " + (pNumber+1));
        System.out.println("Enter Quantity or -1 to Quit");
        pQuantity = productTotal.nextInt();
        cost = 6.87;
        totalcost = totalcost + (cost*pQuantity);
        System.out.println("Current total cost: " + totalcost);
        pNumber++;
    case -1: //declare case for -1 to break out of while loop
        ****pNumber = -1; //set condition for pNumber to break out of loop with input of -1.
        pQuantity = -1; //set condition for pQuantity to break out of loop with input of -1.****
    break; //when condition is met (-1 as input) break out of while loop.
    }
        System.out.println("Total cost-->" +totalcost); //print out the final total cost
    }

}

}

Answer 1

switch 语句中不需要大小写 -1。相反，您可以将 pQuantity > 1 的条件添加到 while 条件中，如下所示：

while ((pNumber >= 0 && pNumber <=5) || ( pQuantity >1)) 

现在，如果你在第一个问题中输入 -1，它退出程序不是因为最后一个 case -1 条件，而是因为 while 循环条件。但是当你对第二个问题（产品数量）输入-1时，它会转到相应的case条件，完成并跳出switch语句，并返回到while循环。它不会进行 case -1 条件检查。