How to use hasNext() from the Scanner class?

Your code does not work because you create a new Scanner object in every recursive call. You should not use recursion for this anyways, do it iteratively instead.

Iterative version

public class Solution {

    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);
        int count = 1;

        while(s.hasNext()) {
            String ns = s.nextLine();
            System.out.println(count + " " + ns);
            count++;
        }
    }
}

Recursive version

public class Solution {

    private Scanner s;

    public static void main(String[] args) {

        s = new Scanner(System.in); // initialize only once
        check(1);
    }

    public static void check(int count) {
        if(s.hasNext()) {
            String ns = s.nextLine();
            System.out.println(count + " " + ns);
            check(count + 1);
        }
    }   
}

Change

if (s.hasNext() == true) {
    String ns = s.nextLine();
    System.out.println(count + " " + ns);
    count++;
    System.out.print(count);
    check(count);
}

to:

while (s.hasNext()) {
    String ns = s.nextLine();
    System.out.println(count + " " + ns);
    count++;
    System.out.print(count);
    check(count);
}

while loops continues until the data exists, where as if checks for only once.