当用户输入的号码不存在时如何在Switch语句中捕获错误

Question

我正在尝试对我的程序进行错误校验，该程序基本上可以用作迷你计算器。但是我不知道如何编写“ Catch”语句来检测用户何时输入不存在的案例编号，在我的案例中为负数或> 4

        System.out.println("Hello user! Which operation would you like to use?");
        System.out.println("1) + \n2) - \n3) * \n4) /");


        Scanner operacijai = new Scanner(System.in);
        int operacija = operacijai.nextInt();


        int n=1;
        do {
        try {
            switch (operacija) {
            case 1:
                addingMethod();
                n=2;
                break;

            case 2:
                subtractingMethod();
                n=2;
                break;

            case 3:
                multiplyingMethod();
                n=2;
                break;

            case 4:
                dividingMethod();
                n=2;
                break;
                    }       
            }
            catch(Exception e) {
                System.out.print("Enter a correct number!");
            }

        } while(n==1);
        operacijai.close();

    } ```

Answer 1

您还可以在default中处理用例处理异常完全取决于您的用例，您还可以创建自定义异常并从默认值抛出类似于：

    System.out.println("Hello user! Which operation would you like to use?");
    System.out.println("1) + \n2) - \n3) * \n4) /");


    Scanner operacijai = new Scanner(System.in);
    int operacija = operacijai.nextInt();


    int n=1;
    do {
    try {
        switch (operacija) {
        case 1:
            addingMethod();
            n=2;
            break;

        case 2:
            subtractingMethod();
            n=2;
            break;

        case 3:
            multiplyingMethod();
            n=2;
            break;

        case 4:
            dividingMethod();
            n=2;
            break;
        default:
            System.out.print("Enter a correct number!")
            throw new CustomException();
        }       
      }
      catch(CustomException e) {
          System.out.print("Enter a correct number!");
      }

    } while(n==1);
    operacijai.close();

}