my main concern with this code as of right now is a missing return statement.
public class stringstuff{ //using charAt public static String Rev
You have two options: either write
public static void /* not String */ ReverseF(String n){
or write return finalString in ReverseF and use
return finalString
ReverseF
public static void main(String[]args){ System.out.println(ReverseF("Hello")); }