Java提取域名或URL中的根域名

【需求】

    域名中包含一级、二级域名等信息，需要提取根域名。

    例如：www.baidu.com 提取出 baidu.com 

               http://write.blog.csdn.net/ 提取出 csdn.net

【实现】

    不多说，直接上代码，主要思路就是通过正则表达式解决。

import java.io.BufferedReader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TopDomainUtil {

private Pattern pattern;

// 定义正则表达式，域名的根需要自定义，这里不全
private static final String RE_TOP = "[\\w-]+\\.(com.cn|net.cn|gov.cn|org\\.nz|org.cn|com|net|org|gov|cc|biz|info|cn|co)\\b()*";

// 构造函数
public TopDomainUtil() {
pattern = Pattern.compile(RE_TOP , Pattern.CASE_INSENSITIVE);
}

public String getTopDomain(String url) {
String result = url;
try {
Matcher matcher = this.pattern.matcher(url);
matcher.find();
result = matcher.group();
} catch (Exception e) {
System.out.println("[getTopDomain ERROR]====>");
e.printStackTrace();
}
return result;
}

public static void main(String[] args) {
TopDomainUtil obj = new TopDomainUtil();

// 示例
String url = "www.baidu.cc";
String res1 = obj.getTopDomain(url);
System.out.println(url + " ==> " + res1);

url = "ac.asd.c.sina.com.cn";
String res2 = obj.getTopDomain(url);
System.out.println(url + " ==> " + res2);

url = "whois.chinaz.com/reverse?ddlSearchMode=1";
String res3 = obj.getTopDomain(url);
System.out.println(url + " ==> " + res3);

url = "http://write.blog.csdn.net/";
String res4 = obj.getTopDomain(url);
System.out.println(url + " ==> " + res4);

url = "http://write.test.org.nz/";
String res5 = obj.getTopDomain(url);
System.out.println(url + " ==> " + res5);
}

}
【代码执行输出】

D:\>javac -encoding utf-8 TopDomainUtil.java

D:\>java TopDomainUtil

www.baidu.cc ==> baidu.cc
ac.asd.c.sina.com.cn ==> sina.com.cn
whois.chinaz.com/reverse?ddlSearchMode=1 ==> chinaz.com http://write.blog.csdn.net/ ==> csdn.net http://write.test.org.nz/ ==> test.org.nz