Question

我认为使用+=总计会对结果求和，但是我重新插入后重置了所有内容。

import java.util.Scanner;
    public class Week3_Lab {
    public static void main(String[]args){
        Scanner input = new Scanner(System.in);



    int product;
        int amount;

        while(true){

        System.out.print("Enter the product number(1-3): ");
        product = input.nextInt();

        if (product == -1){

            break;
        }

        System.out.print("Enter the total amount of product: ");
        amount = input.nextInt();

        num(product, amount);
        }


    }


    public static int num(int product , int amount){
        double total_1 = 0;
        double total_2 = 0;
        double total_3 = 0;

        switch (product){

        case 1 :
        total_1 += amount * 2.98;
        break;

        case 2 : 
        total_2 += amount * 4.50;
        break;

        case 3 : 
        total_3 += amount * 9.98;
        break;

    }
        System.out.println("The total of product 1 is : "+ total_1);
        System.out.println("The total of product 2 is : "+ total_2);
        System.out.println("The total of product 3 is : "+ total_3);

         return product;

    }
    }

Answer 1

您的变量total_1, total_2 and total_3是本地的，不在方法调用之间共享，因此每个调用都被初始化为0。如果您不希望发生这种情况，请在方法体外定义它们。

static double total_1=0;
static double total_2=0;
static double total_3=0;

public static int num(int product , int amount){
    switch (product){
        //...
    }
//...
}

Answer 2

您已将total_1初始化为0，因此输出的程序只是(amount * 2.98)，如下所示：

total_1 = 0 + (amount * 2.98);

同样的概念也适用于total_2和total_3。

交换机情况下（+ =）的功能无效

2 个答案: