Something

public static void main(String[] args) throws IOException {
        boolean backAndforth = true;
        BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
        while (input != ".") {
            System.out.print("Enter an adjective (all lower-case) or type . to exit:");
            System.out.flush();
            input = stdin.readLine();
            if (backAndforth) {
                System.out.println("(using SimpleString)    " + input + " -- " + comparative(new SimpleString(input)));
                backAndforth = false;
            }
            else {
                System.out.println("(using CharArray)    " + input + " -- " + comparative(new CharArray(input)));
                backAndforth = true;
            }
        }
    }