The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
One of the most useful pieces of information you can get from a network interface is the list of IP addresses that are assigned to it. You can obtain this information from a NetworkInterface
instance by using one of two methods. The first method, getInetAddresses()
, returns an Enumeration
of InetAddress
. The other method, getInterfaceAddresses()
, returns a list of
java.net.InterfaceAddress
instances. This method is used when you need more information about an interface address beyond its IP address. For example, you might need additional information about the subnet mask and broadcast address when the address is an IPv4 address, and a network prefix length in the case of an IPv6 address.
The following example program lists all the network interfaces and their addresses on a machine:
import java.io.*; import java.net.*; import java.util.*; import static java.lang.System.out; public class ListNets { public static void main(String args[]) throws SocketException { Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces(); for (NetworkInterface netint : Collections.list(nets)) displayInterfaceInformation(netint); } static void displayInterfaceInformation(NetworkInterface netint) throws SocketException { out.printf("Display name: %s\n", netint.getDisplayName()); out.printf("Name: %s\n", netint.getName()); Enumeration<InetAddress> inetAddresses = netint.getInetAddresses(); for (InetAddress inetAddress : Collections.list(inetAddresses)) { out.printf("InetAddress: %s\n", inetAddress); } out.printf("\n"); } }
The following is sample output from the example program:
Display name: TCP Loopback interface Name: lo InetAddress: /127.0.0.1 Display name: Wireless Network Connection Name: eth0 InetAddress: /192.0.2.0