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;
	}