Question

我目前正在键入一个简单的程序，其中包含方法和一个开关案例，该案例使用人的响应通过调用相应的方法来添加，乘，减或除，具体取决于用户的方法输入。

我有三个问题：

我的切换声明不起作用
程序要求我初始化变量answer，但当我将其设置为0时，无论方程是什么，我总是得到0的响应。
我的方法没有返回答案，但是当我从方法中输出时，它会显示正确的答案。以下是我的代码和编译错误。

import java.util.Scanner;

public class Math {

    public static void main (String[] args){

        //used to import scanner class for keyboard use
        Scanner kb = new Scanner(System.in);

        //used to hold value of first number
        int a;
        //used to hold the value of the second number
        int b;
        //used to hold value for response of line 29
        int d;

        //out put message to user
        System.out.println("Please enter a whole number between 0 and 100.");
        a = kb.nextInt();

        if (a > 100) {
            System.out.println("The number you entered did not match the criteria, please run the program again.");
            System.exit(0);
        } else
            System.out.println("Please enter another whole number between 0 and 100.");

        b = kb.nextInt();

        if (b > 100) {
            System.out.println("The number you entered did not match the criteria, please run the program again.");
            System.exit(0);
        } else
            System.out.println("What would you like to do with these two numbers?");

        System.out.println("1=Add, 2=Subtraction, 3=Multiply, 4=Divide");

        d = kb.nextInt();

          switch(d){

          case '1':
              System.out.println("you choose addition!");
              add(a, b);
              break;

          case '2':
              subtract(a, b);
              break;

          case '3':
              multiply(a, b);
              break;

          case '4':
              divide(a, b);
              break;

          default:
              System.out.println("You did not make a valid choice, please run the program again.");
              System.exit(0);
          }
    }

    public static int add(int x, int y){
        int answer;
        answer = x+y;
        return answer;
    }

    public static int subtract(int x, int y){
        int answer = x-y;
        return answer;
    }

    public static int multiply(int x, int y){
        int answer = x*y;
        return answer;
    }

    public static int divide(int x, int y){
        int answer = x/y;
        return answer;
    }

}

Answer 1

你需要让switch语句如下所示：

switch (d)
{
    case 1: // look for the int 1 not the char '1'
        System.out.println("you choose addition!");

        // also, print out what the methods are returning:
        System.out.println("The answer is: " + add(a, b));
        break;
    case 2:
        subtract(a, b);
        break;
    case 3:
        multiply(a, b);
        break;
    case 4:
        divide(a, b);
        break;
    default:
        System.out.println("You did not make a valid choice, please run the program again.");
        System.exit(0);
}

附注：

在你的除法中你正在进行整数除法，这是不精确的。您可能需要考虑使用双精度进行除法并返回双精度。

例如，

public static double divide (int x, int y)
{
    double answer = (double) x / (double) y;
    return answer;
}

在退出程序之前，您还应该close退出扫描程序。

Answer 2

您永远不会设置答案变量。你的add，sub，multiple和divide方法返回一个int，但你从不指定它来回答。例如：

int answer = 0;
answer=add(a, b);

使用switch case语句

2 个答案: