public static void writeBackward(String s, int size) {
  if (size > 0) {
    // write the last character
    System.out.println(s.substring(size-1, size));
    writeBackward(s, size - 1); // write rest
  } // end if
} // end writeBackward

public static void writeBackwardIter(String s, int size) {
  // Iterative version.
  while (size > 0) {
    System.out.println(s.substring(size-1, size));
    --size;
  } // end while
} // end writeBackward