How to return integer with String with recursion

My task was : I have to return string "." many times as integer n was given. but also I have to return the first n all this using recursion how do I do it?

My code :

private static String recString(final int i) {
      return (i==0 ? "" : i>0 ? recString(i)+ recString(i-1)+"." : "."+recString(i+1));
}