java - 如何让错误显示出来

Question

public void runMenu() {
        int x = 1;
        Scanner Option = new Scanner(System.in);
        int Choice = 0;

        do {
            try {
                System.out.println("Choose Option");
                System.out.println("");
                System.out.println("1: Create Account");
                System.out.println("2: Check Account");
                System.out.println("3: Take Action");
                System.out.println("4: Exit");

                System.out.println("Please choose");
                Choice = Option.nextInt();

                switch (Choice) //used switch statement instead of If else because more effective
                {
                    case 1:
                        CreateAccount();
                        break;   //breaks iteration
                    case 2:
                        selectAccount();
                        break;
                    case 3:
                        break;
                }
            } catch (Exception e) {
                System.out.println("Cant do that");
            }
        } while (Choice < 4);
        System.out.println("Bye");
    }

异常处理不起作用，例如如果我输入超出范围(例如 5)，它应该显示类似“不能这样做”的内容。我应该输入一个 if 语句来定义条件 if 那么我该怎么做呢？现在，如果我输入错误的 key ，它只会打印“再见”。

Answer 1

您的问题是由于您的循环 while Choice < 4 .

您应该将循环更改为 while(true);然后在 switch case 内创建一个 case 4，使用 System.exit(0) 退出程序

然后包含一个默认值，该默认值将通知用户他们输入了无效值

public void runMenu() {

    int x = 1;
    Scanner Option = new Scanner (System.in);
    int Choice = 0; 

  do{  
    try{



           System.out.println("Choose Option");
             System.out.println("");
             System.out.println("1: Create Account");
             System.out.println("2: Check Account");
             System.out.println("3: Take Action");
             System.out.println("4: Exit");



        System.out.println("Please choose");
         Choice= Option.nextInt();  




    switch (Choice)  //used switch statement instead of If else because more effective
    {
    case 1:

        CreateAccount();
        break;   //breaks iteration




    case 2: 

        selectAccount();


        break;

    case 3:


        break;
    case 4:
        System.out.println("Bye"); 
        System.exit(0);
    default:
        System.out.println("Invalid Entry");
        break;


} 
}



catch (Exception e){
    System.out.println("Cant do that"); 
}
} while (true);

}