Reverse a string using Helper Method Recursion

// package whatever; // don't place package name!

import java.io.*;
/**
 *  2c. Reverse a string using Helper Method Recursion
 *
 *  Input:   String
 *  Output:  String
 *
 *  Example: String greeting = 'hello';
 *          ReverseString.compute(greeting) => 'olleh'
 */
class ReverseString {

    public static void main (String[] args) {
     String str = "hello";
     System.out.println(compute(str));
      }

    public static String compute(String str) {
      //if string is empty or contains 1 character, return string
      if(str.length() <=1 ){
        return str;
      }
      //to help w/visualization of recursive call
      System.out.println(str.substring(1));
      //substring returns string from element 1 - string.length()
      return compute(str.substring(1)) + str.charAt(0);
    }
}