C#使用正则判断IP地址

C#使用正则判断一个字符串是否为IP地址：

private boolean isIp(String ip) {
    String rex =
            "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                    "([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";
    Pattern pattern = Pattern.compile(rex);
    Matcher matcher = pattern.matcher(ip);
    return matcher.find();
}