Java 为输出获取0而不是预期的计算

我的产出一直是0.0。我不知道我做错了什么。任何帮助都将不胜感激

我的前几个部分的用户输入是正确的，并且数字显示正确。只有在求总数和后续的数学运算时，我才得到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!");

    }
}

---

如果您的

语句被破坏，则最后一个语句始终*保证触发，为您提供
0.0

您应该将它们分组为
if-else-if-else
语句，例如：

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，您的合计报表也错误-您只打印
tax
值，而不是
total+tax
值

*：如果您选择4，那么它将实际工作。但这是因为4的选择是附加在
else
上的，您也可以这样做：

    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;
    }

给变量产品值null（0），然后给它一个新的值进一步向下的代码。
因此，投入更多的调试输出，并准确跟踪哪一行“丢失”您的值…请发布高质量的代码-这个缩进伤害眼睛@基蒂普尔：修正了压痕。使用IntelliJ或任何自动格式化IDE真的不难，那么花两分钟做这件事有什么害处呢？你知道，如果能在其功能中添加简单的文本缩进，那就太好了。这是一段有点难看的代码，但并不比简单的control-K缩进4操作糟糕多少。@Makoto如果它很简单，请在这里发布代码之前执行它。你在寻求帮助，而不是我。此时，你正在检查每一个可能的块，无论是否设置了值。比if-else-if-else甚至
开关更不理想。