input a string of lowercase. recursively remove instances of doubled characters

ReduceString.java

/**
 *  TT 2017-10-20
 *
 *  solution for "Super Reduced String"
 *  https://www.hackerrank.com/challenges/reduced-string
 *
 *  similar "brute force" ways:
 *
 *  with stringbuilder
 *  https://github.com/ebolat/HackerRank/blob/master/Algorithms/Strings/Super%20Reduced%20String/Solution.java
 *
 *  with string
 *  https://codereview.stackexchange.com/questions/150921/super-reduced-string
 *
 *  Better:
 *  =======
 *  "diy" stack of char
 *  (ans to question above)
 *  https://codereview.stackexchange.com/a/150946
 *
 *  actual stack of Character:
 *  https://github.com/rshaghoulian/HackerRank_solutions/blob/master/Algorithms/Strings/Super%20Reduced%20String/Solution.java
 *
 *
 */

import java.util.Scanner;

public class ReduceString {

    static String super_reduced_string(String s) {
        // Complete this function
        String reduced = s;
        for (int i = 0; i < s.length() - 1; i++) {  // up to 2nd-last char

            // System.out.printf("i= %d length= %d s= %s%n", i, s.length(), s);

            if (s.charAt(i) == s.charAt(i + 1)) {
                // remove i,i+1
                // System.out.printf("remove from pos %d: %c%c%n", i, s.charAt(i), s.charAt(i + 1));
                reduced = s.replace(s.substring(i, i + 2), "");
                // System.out.println("reduced is " + reduced);

                reduced = super_reduced_string(reduced);
                // not written on one line, to examine the effect of having no
                // return statement here -
                // recursive calls stack, when starting to unwind, execution returns to this point,
                // skipping the start of the for loop, so that i ends up exceeding string length
                // and the reduced string grows back to an earlier state (! wrong - although it can
                // produce valid strings as well)
                return reduced;

                // return super_reduced_string(reduced);
            }
        }
        reduced = reduced.equals("") ? "Empty String" : reduced;
        return reduced;
    }

    public static void main(String[] args) {
        // Scanner in = new Scanner(System.in);
        // String s = in.next();
         String s = "aaabccddd";
        // String s = "abcdefgh";
        // String s = "aabbcc";
        String result = super_reduced_string(s);
        System.out.println(result);
    }
}