Cacher is the code snippet organizer for pro developers

String strangeCode(int s, int e) {
    char prev = 'a';
    String res = "";
    while (s < e - 1) {
        s++;
        e--;
        if ("".equals(res)) res += "a";
        else {
            if (prev == 'a') {
                res += "b";
                prev = 'b';
            }
            else {
                res += "a";
                prev = 'a';
            }
        }
    }
    return res;
}