Using CoderPad, why do I get a NoSuchElementException using a Scanner on System.in?

I am preparing for an interview I have in a few days. I was told that I should familiarize myself with CoderPad since that is the collaborator I will be interviewed with. However, I was in the middle of answering a question when I realized I could not read input from System.in using the Scanner class.

For example, running the following:

import java.io.*;
import java.util.*;

/*
 * To execute Java, please define "static void main" on a class
 * named Solution.
 *
 * If you need more classes, simply define them inline.
 */

class Solution {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    String s = in.next();
    System.out.println(s);
  }
}

Gives me the message:

Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Scanner.java:862)
    at java.util.Scanner.next(Scanner.java:1371)
    at Solution.main(Solution.java:14)

What's going on here?

Copyright Notice：Content Author:「youngrrrr」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/34277694/using-coderpad-why-do-i-get-a-nosuchelementexception-using-a-scanner-on-system