Thread: Some problem with "Main"?

I'm kind of a coding newb but i managed to make this:

import java.util.Scanner;
 
public class ReactionGame {
 
	public static void main(String[] args) {
 
		int Time = 0;
		String s = null;
		@SuppressWarnings("resource")
		Scanner NewScanner = new Scanner(System.in);
		System.out.println("Type K and press enter when STOP appears");
		Delay(1000);
		System.out.println("STOP");
		while (s.equalsIgnoreCase("k")) {
		String k1 = NewScanner.nextLine();
		s = k1;
		Time ++;
	}
		System.out.println("Your time was:" + Time);
 
	}
 
	private static void Delay(int i) {
		try {
 
			  Thread.sleep(100L);
 
			}
 
			catch (Exception e) {}  
	}
}

Its supposed to do this:
Say: when STOP appears enter k and enter!
then after some time
STOP
and then you must type in K+Enter
Then it will show your Score...
But it gives this error:

Type K and press enter when STOP appears
STOP
Exception in thread "main" java.lang.NullPointerException
at ReactionGame.main(ReactionGame.java:14)

I don't know what i did wrong and even eclipse doesnt give me an answer.

Kind regards,
Niels