// "foobar" -> "fobar"
// "sstrringg" -> "string"
// "ssss" -> "s"
private static String removeDuplicates(String str) {
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < str.length(); i++) {
        if (i + 1 == str.length()) {
            sb.append(str.charAt(i));
        } else {
            char curChar = str.charAt(i);
            char nexChar = str.charAt(i + 1);

            if (curChar != nexChar) {
                sb.append(curChar);
            }
        }
    }

    return sb.toString();
}