Question

我继续为我的输出获得0.0。我不知道我做错了什么。任何帮助将不胜感激。

前几节的用户输入正常，数字正确显示。它只是在要求我得到的总数和后续数学时得到0.0,0.0,0.0

import java.util.Scanner;

public class CoffeeShop {
    public static void main(String[] args) {

        //Welcome Message and name prompt
        String username;

        System.out.println("What is your name?");
        Scanner keyboard = new Scanner(System.in);
        username = keyboard.next();
        System.out.println("Welcome to the Java Byte Code Coffee Shop," + username + "!");

        //Menus
        System.out.println("Here is our menu.");
        System.out.println("1. Coffee $1.50");
        System.out.println("2. Latte $3.50");
        System.out.println("3. Cappuccino $3.25");
        System.out.println("4. Espresso $2.00");

        //What item do they want?
        int product_Number;
        System.out.println("Please enter the item number.");
        Scanner item = new Scanner(System.in);
        product_Number = item.nextInt();
        System.out.println("You selected item " + product_Number);
        double product;

        if (product_Number == 1) {
            product = 1.50;
        }
        if (product_Number == 2) {
            product = 3.50;
        }
        if (product_Number == 3) {
            product = 3.25;
        }
        if (product_Number == 4) {
            product = 2.00;
        } else {
            product = 0.00;
        }

        //Quantity of item
        int quantity;
        System.out.println("How many would you like?");
        Scanner amount = new Scanner(System.in);
        quantity = amount.nextInt();
        System.out.println("You want " + quantity + " of them!");
        //Testing Product
        double total = quantity * product;
        System.out.println("Total before discount and tax is " + total);

        double nuTotal;
        //Discount/Tax
        if (total >= 10) {
            nuTotal = total - (total * .1);
        } else {
            nuTotal = total;
        }
        System.out.println("Your total with discount is " + nuTotal);
        double totalTax = nuTotal * .07;
        System.out.println("Your total with tax is " + totalTax);

        System.out.println("Thank you " + username + "! Please stop by again!");

    }
}

Answer 1

您的if声明已被删除 - 我们始终保证最后一个声明会被触发，为您提供0.0。

您应该将它们组合在一起作为if-else if-else语句，如下：

if (product_Number == 1) {
    product = 1.50;
} else if (product_Number == 2) {
    product = 3.50;
} else if (product_Number == 3) {
    product = 3.25;
} else if (product_Number == 4) {
    product = 2.00;
} else {
    product = 0.00;
}

此外，您的总陈述也是错误的 - 您只打印tax值，而不是total + tax值。

^{*：如果您选择4，那么它实际上会起作用。但那是因为选择4附加到else。}

Answer 2

你也可以这样做：

    double product = 0;

    if (product_Number == 1) {
        product = 1.50;
    }
    if (product_Number == 2) {
        product = 3.50;
    }
    if (product_Number == 3) {
        product = 3.25;
    }
    if (product_Number == 4) {
        product = 2.00;
    }

将变量产品值赋予null（0），然后在代码的下方给它一个新值。

输出为0而不是预期计算

2 个答案: