Question

System.out.println("\nHow many sticks do you want?");
    while(sticks==0){
        try{
            sticks=startInput.nextInt();
        }catch(InputMismatchException e){
            sticks=0;
            System.out.println("Please enter a valid number.");
        }
        sticks=startInput.nextInt();
    }

我尝试做什么：它要求一个int但是当有人输入chars时它应该再次询问而不是崩溃。

Answer 1

第二个sticks=startInput.nextInt();不在try-catch块内，因此如果您放置更多字符，它将再次失败。由于您没有自己处理异常，异常会冒出来并最终导致应用程序崩溃。

编辑：根据你的评论，这取决于。假设您希望在用户提供0作为问题答案的时候关闭您的应用程序，您可以这样做：

System.out.println("\nHow many sticks do you want?");
    while(sticks >= 0){
        try{
            sticks=startInput.nextInt();
        }catch(InputMismatchException e){
            sticks=0;     //Any value which is not 0 will not break your loop. This will be re-populated when the user will supply the number again.
            System.out.println("Please enter a valid number.");
        }
    }

如果您希望您的应用程序停止（这似乎不太可能）来自您的代码：

System.out.println("\nHow many sticks do you want?");
    while(sticks==0){
        try{
            sticks=startInput.nextInt();
        }catch(InputMismatchException e){
            sticks=0;     //The 0 will break your while loop, exiting your application gracefully.
            System.out.println("Please enter a valid number.");
        }
    }

这是可行的：

private static int sticks;
    private static Scanner startInput;

    public static void main(String[] args) {
        sticks = 0;
        startInput = new Scanner(System.in);        
        while (sticks >= 0) {            
            try {
                System.out.println("How many sticks do you want?");
                sticks = Integer.parseInt(startInput.nextLine());
            } catch (NumberFormatException e) {
                sticks = 0;     //Any value which is not 0 will not break your loop. This will be re-populated when the user will supply the number again.
                System.out.println("Please enter a valid number.");
            }
        }
    }

Answer 2

似乎你错过了把循环放在这里，检查下面的代码：

while(true){
    System.out.println("\nHow many sticks do you want?");
        while(sticks==0){
            try{
                sticks=startInput.nextInt();
            }catch(InputMismatchException e){
                sticks=0;
                System.out.println("Please enter a valid number.");
            }
        }
    }

Java抛出了我认为不应该的异常

2 个答案: