How to use Scanner to accept only valid int as input

Question

I\'m trying to make a small program more robust and I need some help with that.

Scanner kb = new Scanner(System.in);
int num1;
int num2 = 0;

System.out.prin         


        

Answer 1

Try this:

    public static void main(String[] args)
    {
        Pattern p = Pattern.compile("^\\d+$");
        Scanner kb = new Scanner(System.in);
        int num1;
        int num2 = 0;
        String temp;
        Matcher numberMatcher;
        System.out.print("Enter number 1: ");
        try
        {
            num1 = kb.nextInt();
        }

        catch (java.util.InputMismatchException e)
        {
            System.out.println("Invalid Input");
            //
            return;
        }
        while(num2

You could try to parse the string into an int as well, but usually people try to avoid throwing exceptions.

What I have done is that I have defined a regular expression that defines a number, \d means a numeric digit. The + sign means that there has to be one or more numeric digits. The extra \ in front of the \d is because in java, the \ is a special character, so it has to be escaped.