Java正则表达式匹配URL中的host

public static String getHost(String url) {
    if (url == null || url.trim().equals("")) {
      return "";
    }
    String host = "";
    Pattern p = Pattern.compile("(?<=//|)((\\w)+\\.)+\\w+(:\\d*)?");
    Matcher matcher = p.matcher(url);
    if (matcher.find()) {
      host = matcher.group();
    }
    return host;
  }