java 提取主域名

import com.google.common.net.InternetDomainName;

public static void main(String[] args) {
    InternetDomainName top = 
        InternetDomainName.from("keyupgrade.spaceforupdate.download").topPrivateDomain();

    System.out.println(top);
  }

比如我写的：

    private String extractDomain(String domain) {
        try {
            return InternetDomainName.from(domain).topPrivateDomain().name();
        } catch (java.lang.IllegalStateException e) {
            String[] levels = domain.split("\.");
//            if (levels.length > 1) {
//                return levels[levels.length - 2] + "." + levels[levels.length - 1];
//            } else {
                return levels[levels.length-1];
//            }
        } catch (java.lang.IllegalArgumentException e){
            String[] levels = domain.split("\.");
            return levels[levels.length-1];
        }
    }

参考：

https://stackoverflow.com/questions/45046265/internetdomainname-and-publicsuffix-list

https://github.com/google/guava/blob/master/guava/src/com/google/common/net/InternetDomainName.java

https://stackoverflow.com/questions/7217271/extract-main-domain-name-from-a-given-url