Java separate digits by space

import java.util.*;
class   AddSpaceToDigits
{
    public static String addSpaceToRight(String s, int n) {
     return String.format("%1$-" + n + "s", s);  
}

public static void main(String args[]) throws Exception {
    Scanner  input=new Scanner(System.in);
    System.out.print("Enter number: ");
    int num=input.nextInt();
    String st=Integer.toString(num);
    String digit[]=st.split("");
    System.out.print(digit[0]);
    for(int i=1;i<digit.length;i++){
    System.out.print(addSpaceToRight(digit[i], 3));
    }
    System.out.println();
}
}

sry i dnt knw arrays yet...i want to solve this from any function...

42339/10000=4.2339take 4 from this