Comment inverser les caractères en utilisant la récursivité en Java

package net.javaguides.corejava.string;
/**
* 
* @author yisu
*
*/
public class UsingRecursion {
static int i = 0;
// Recursive function to reverse a string in Java using static variable
private static void reverse(char[] str, int k) {
// if we have reached the end of the string
if (k == str.length)
return;
// recurse for next character
reverse(str, k + 1);
if (i <= k) {
char temp = str[k];
str[k] = str[i];
str[i++] = temp;
}
}
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// convert string into a character array
char[] A = str.toCharArray();
// reverse character array
reverse(A, 0);
// convert character array into the string
return String.copyValueOf(A);
}
public static void main(String[] args) {
String str = "Java Guides";
// string is immutable
str = reverse(str);
System.out.println("Reverse of the given string is : " + str);
}
}

Reverse of the given string is : sediuG avaJ