这款扫描仪出了什么问题？

Question

So I have some Java code with a Scanner. What am I doing wrong as I am getting errors.

// Creates a "scanner" for the input
Scanner readInput = new Scanner(System.in);

// Print out random integer and open close message.
System.out.println("Printing Random Numbers between 1-200: ");
int guess = readInput.nextInt();

Errors (I am fairly new to Java, well I coded quite a bit like 4-5 years ago. but forgot):

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at main.files.mian.main(mian.java:30)

Answer 1

If you type in anything other than a number (integer), your program crashes. The following code checks if it's able to convert the input into a int. If yes, everything is ok, otherwhise the error will be printet, but the program doesn't crash.

        // Creates a "scanner" for the input
        Scanner readInput = new Scanner(System.in);

        // Print out random integer and open close message.
        System.out.println("Printing Random Numbers between 1-200: ");
        try {
            int guess = readInput.nextInt();
        } catch (InputMismatchException e) {
            System.err.println("You didn't enter a number.");
        }