TheNetworkInterface
class has no public constructor. Therefore, you cannot just create a new instance of this class with thenew
operator. Instead, the following static methods are available so that you can retrieve the interface details from the system:getByInetAddress()
,getByName()
, andgetNetworkInterfaces()
. The first two methods are used when you already know the IP address or the name of the particular interface. The third method,getNetworkInterfaces()
returns the complete list of interfaces on the machine.Network interfaces can be hierarchically organized. The
NetworkInterface
class includes two methods,getParent()
andgetSubInterfaces()
, that are pertinent to a network interface hierarchy. ThegetParent()
method returns the parentNetworkInterface
of an interface. If a network interface is a subinterface,getParent()
returns a non-null value. ThegetSubInterfaces()
method returns all the subinterfaces of a network interface.The following example program lists the name of all the network interfaces and subinterfaces (if any exist) on a machine.
The following is sample output from the example program:import java.io.*; import java.net.*; import java.util.*; import static java.lang.System.out; public class ListNIFs { public static void main(String args[]) throws SocketException { Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces(); for (NetworkInterface netIf : Collections.list(nets)) { out.printf("Display name: %s\n", netIf.getDisplayName()); out.printf("Name: %s\n", netIf.getName()); displaySubInterfaces(netIf); out.printf("\n"); } } static void displaySubInterfaces(NetworkInterface netIf) throws SocketException { Enumeration<NetworkInterface> subIfs = netIf.getSubInterfaces(); for (NetworkInterface subIf : Collections.list(subIfs)) { out.printf("\tSub Interface Display name: %s\n", subIf.getDisplayName()); out.printf("\tSub Interface Name: %s\n", subIf.getName()); } } }Display name: bge0 Name: bge0 Sub Interface Display name: bge0:3 Sub Interface Name: bge0:3 Sub Interface Display name: bge0:2 Sub Interface Name: bge0:2 Sub Interface Display name: bge0:1 Sub Interface Name: bge0:1 Display name: lo0 Name: lo0