IPV6 Java Regular expression example

Pattern

private static final Pattern IPV6REGEX = Pattern.compile(""
        + "^(((?=(?>.*?::)(?!.*::)))(::)?([0-9A-F]{1,4}::?){0,5}"
        + "|([0-9A-F]{1,4}:){6})(\\2([0-9A-F]{1,4}(::?|$)){0,2}|((25[0-5]"
        + "|(2[0-4]|1\\d|[1-9])?\\d)(\\.|$)){4}|[0-9A-F]{1,4}:[0-9A-F]{1,"
        + "4})(?<![^:]:|\\.)\\z", Pattern.CASE_INSENSITIVE);

Example

package com.pretech;

import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.UnknownHostException;
import java.util.regex.Pattern;

public class Ipv6Example {
   private static final Pattern IPV6REGEX = Pattern.compile(
         "" + "^(((?=(?>.*?::)(?!.*::)))(::)?([0-9A-F]{1,4}::?){0,5}" 
+ "|([0-9A-F]{1,4}:){6})(\\2([0-9A-F]{1,4}(::?|$)){0,2}|((25[0-5]"
               + "|(2[0-4]|1\\d|[1-9])?\\d)(\\.|$)){4}|[0-9A-F]{1,4}:[0-9A-F]{1," 
+ "4})(?<![^:]:|\\.)\\z",
         Pattern.CASE_INSENSITIVE);

   public static void main(String[] args) {

      URL url;
      int i1, i2;

      try {
         url = new URL("http://[FF01:0:0:0:0:0:0:0101]");
         String originalHostName = url.getHost();

         System.out.println(originalHostName);
         if (originalHostName.startsWith("[") && originalHostName.endsWith("]")) {

            i1 = originalHostName.indexOf("[");

            originalHostName = originalHostName.substring(i1 + 1);

            i2 = originalHostName.lastIndexOf("]");

            originalHostName = originalHostName.substring(0, i2);

            if (IPV6REGEX.matcher(originalHostName).matches()) {

               System.out.println(url + " is a ipv6 address");
               String hostName = InetAddress.getByName(originalHostName).getHostAddress().toLowerCase();
               if (hostName.contains(":")) {
                  hostName = "[" + hostName + "]";
               }

            }
         }

      } catch (MalformedURLException | UnknownHostException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }

   }

}

Output

[FF01:0:0:0:0:0:0:0101]
http://[FF01:0:0:0:0:0:0:0101] is a ipv6 address