java - Endless loop while using "try and catch " block inside a "while loop"

Question

My program has an endless loop, when I use try and catch block in a while loop.

import java.util.*;
class Try
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        while(true)
        {
            try {
                System.out.println("Enter a no ");
                int s=sc.nextInt();
            } catch(Exception e) {
                System.out.println("Invalid input try again");
            }
        }
    }
}

When I input an integer, it runs fine and asks for another input, but when I input a char, it goes for endless loop. Why is this so?

Answer 1

Your program enters an infinite loop when an invalid input is encountered because nextInt() does not consume invalid tokens. So whatever token that caused the exception will stay there and keep causing an exception to be thrown the next time you try to use nextInt().

This can be solved by putting a nextLine() call inside the catch block to consume whatever input was causing the exception to be thrown, clearing the input stream and allowing the user to continue trying.