// For loop 
public static void main(String[] args) {
   Scanner scan = new Scanner(System.in);
   for(int i = 1; scan.hasNext()== true; i++){
       System.out.println(i + " " + scan.nextLine());
   }
}

// While loop System
public static void main(String[] args) {
   Scanner scan = new Scanner(System.in);
   int i = 0;
   while(scan.hasNext()){
       i++;
       System.out.println(i + " " + scan.nextLine());
   }
}

Both Loop working for me

here is my solution

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

public class Solution {

    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        String a;
        int i=1;
       while(in.hasNext())
           {
           a=in.nextLine();
           System.out.println(i+" "+a);
           i++;
       }
    }
}

for all the people who are saying that how will the scanner.hasNext() condition will come false,then listen folks. it is not described here but the input is coming from a text file and the scanner object starts to read from the top and reads upto the end. when the end of the text file comes as there is nothing to read the condition become false and loop brakes.

   Scanner Scan = new Scanner(System.in);
   int Count = 0;

   while(Scan.hasNext()) 
       System.out.println(++Count + " " + Scan.nextLine() );