Getting valid input with Scanner

Question

I want to request that a user enter an integer from the keyboard using Scanner's nextInt metod, catch the InputMismatchException, and loop until a correct value is entered.
My attempt loops forever when the input is incorrect. It repeats the prompt but immediately goes to the catch clause. Can anyone shed some light on this for me - and point me in the direction of a solution?
Here is the code.
import java.util.*;
public class NumberFormatDemo
   public static void main (String[] arg)
       boolean goodInput = false;
       Scanner in = new Scanner(System.in);
       int age = 0;  //keep the compiler happy
       //loop until user gets it right
       while(!goodInput)
          try
             System.out.print("Please enter your age: ");
             age = in.nextInt();
             goodInput = true;
             System.out.println("You are " + age + " years old");
          catch(InputMismatchException e)
             System.out.println("The data you entered is invalid. Please try again.");
}Thanks,
kob

Answer 1

The data that the user entered is still being "pointed" at by the scanner. To fix this, try adding an "in.next()" statement in your exception handling block.
public class NumberFormatDemo {
    public static void main(String[] arg) {
        Scanner in = new Scanner(System.in);
        while (true) {
            try {
                System.out.print("Please enter your age: ");
                System.out.println("You are " + in.nextInt() + " years old");
                break;
            catch(InputMismatchException e) {
                System.out.println(in.next() + " is an invalid age. Please try again.");
}