java 正则表达式 匹配主域名

String url = "http://anotherbug.blog.chinajavaworld.org.cn/entry/4545/0/";
Pattern p = Pattern.compile("(?<=http://|\\.)[^.]*?\\.(?:com\\.cn|net\\.cn|org\\.cn|com|net|org|cn|biz|info|cc|tv)",Pattern.CASE_INSENSITIVE);

//获取完整的域名
// Pattern p =Pattern.compile("[^//]*?\\.(com|cn|net|org|biz|info|cc|tv)", Pattern.CASE_INSENSITIVE);
Matcher matcher = p.matcher(url);
matcher.find();
System.out.println(matcher.group());