Question

I currently have a simple function (posted below) which asks the user a question and expects to have an integer answer.

Is there a way to make java restrict the characters that can be entered into the console i.e. only allow numbers to be entered.

I know there are simple ways to do this in other programming languages but How should I go about doing this in java and implementing it into my function?

    static int questionAskInt(String question)
{
    Scanner scan = new Scanner (System.in);
    System.out.print (question+"\n");
    System.out.print ("Answer: ");
    return scan.nextInt();
}

Answer 1

Using Scanner.hasNextInt, and while loop, you can restrict the user to give input, until it passes an integer value.

while (!scan.hasNextInt()) {
    System.out.println("Please enter an integer answer");
    scan.next();
} 
return scan.nextInt();

or, you can also give a certain number of chances (so that it does not go into infinite loop, by using a count variable: –

int count = 3;

while (count > 0 && !scan.hasNextInt()) {
    System.out.println("Please enter an integer answer");
    System.out.println("You have " + (count - 1) + "more chances left.");
    count--;
    scan.next();
}

if (count > 0) {
    return scan.nextInt();
}

return -1;