使用 Scanner.nextInt()时，输入应为整数.输入其他任何内容(包括实数)都会引发 InputMismatchException .为了确保无效输入不会停止您的程序，请使用try/catch处理异常:

When you're using Scanner.nextInt() the input is expected to be an integer. Inputting anything else, including a real number, will throw an InputMismatchException. To make sure invalid input doesn't stop your program, use a try/catch to handle the exception:

int num;
try {
    num = sc.nextInt();
    // Continue doing things with num
} catch (InputMismatchException e) {
    // Tell the user the error occured
}