JAVA - regulárne výrazy

private void processInput() {
        final String regex = "([OM])([A-M])([1-8]) ";
        // final String regex = "([OM])";

        String s = readLine();
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(s);

        if (matcher.matches()) {
           if (matcher.group(1).equals("O"))
            System.out.println("ano");

        }else System.out.println("nie");
    }