gistfile1.java

import java.net.*;
import java.util.*;
import java.util.Enumeration;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
class InetAddressTest
{
        private static final String IPADDRESS_PATTERN =
                "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
                "([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";

        public static InetAddress getCurrentEnvironmentNetworkIp() {
                Enumeration<NetworkInterface> netInterfaces = null;
                try {
                    netInterfaces = NetworkInterface.getNetworkInterfaces();
                } catch (SocketException e) {
                }

                List<InetAddress> addresses = new ArrayList<InetAddress>();

                while (netInterfaces.hasMoreElements()) {
                    NetworkInterface ni = netInterfaces.nextElement();
                    Enumeration<InetAddress> address = ni.getInetAddresses();
                    while (address.hasMoreElements()) {
                        InetAddress addr = address.nextElement();
                        if(Pattern.compile(IPADDRESS_PATTERN).matcher(addr.getHostAddress()).matches() && !addr.isLoopbackAddress()) {
                                addresses.add(addr);
                        }
                    }
                }

                try {
                        for (InetAddress addr : addresses) {
                                if(addr.getHostAddress().equals(InetAddress.getLocalHost().getHostAddress())) {
                                        return InetAddress.getLocalHost();
                                }
                        }
                } catch(Exception e) {
                        return null;
                }


                if(addresses.size() == 0) {
                        return null;
                }

                return addresses.get(0);
        }

        public static void main(String args[]) throws UnknownHostException {
                InetAddress Address = InetAddress.getLocalHost();
                System.out.println(Address);
                System.out.println(getCurrentEnvironmentNetworkIp());
                System.out.println(Address.getCanonicalHostName());
                System.out.println(getCurrentEnvironmentNetworkIp().getCanonicalHostName());
        }
}