public static void main(String[] args) {
        String str = "aaaaa<img src=\"http://ctffamily.com/images/f/12.gif\" width=\"24\" " +
                "height=\"24\">nnnnnnnn<img src=\"http://ctffamily.com/images/f/6.gif\" " +
                "width=\"24\" height=\"24\">bbbbbbbbbbbbbbbbbb";
        str = str.replaceAll("<img.*?src=.*?/([^/]*?)\\.gif.*?>", "$1");
        System.out.println(str);
    }