public class NetInfo { public static void main(String[] args) { new NetInfo().say(); } public void say() { try { java.net.InetAddress i = java.net.InetAddress.getLocalHost(); System.out.println(i); // name and IP address System.out.println(i.getHostName()); // name System.out.println(i.getHostAddress()); // IP address only } catch(Exception e){e.printStackTrace();} } }
The output:
> java NetInfo realone/209.142.72.112 realone 209.142.72.112
To list all the interfaces available on a workstation:
import java.net.*; import java.util.*; import java.io.*; import java.nio.*; public class IPAdress { public void getInterfaces (){ try { Enumeration e = NetworkInterface.getNetworkInterfaces(); while(e.hasMoreElements()) { NetworkInterface ni = (NetworkInterface) e.nextElement(); System.out.println("Net interface: "+ni.getName()); Enumeration e2 = ni.getInetAddresses(); while (e2.hasMoreElements()){ InetAddress ip = (InetAddress) e2.nextElement(); System.out.println("IP address: "+ ip.toString()); } } } catch (Exception e) { e.printStackTrace(); } } public static void main(String[] args) { IPAdress ip = new IPAdress(); ip.getInterfaces(); } }
The output:
> java IPAdress Net interface: lo IP address: /127.0.0.1 Net interface: eth0 IP address: /194.168.0.1 Net interface: eth1 IP address: /164.254.147.20 Net interface: ppp0 IP address: /64.68.115.69
Windows
A “low-tech” way to get the computer name (can be useful if there is no network card) is to use the environment variable COMPUTERNAME (at least on modern Windows installation).
[JDK1.4 or less] Pass it to your JVM as java -Dcomputername=”%COMPUTERNAME%” … and then get the value with System.getProperty(“computername”)
[JDK1.5 or more] You can extract environment variables directly with System.getenv(“COMPUTERNAME”)
Done! Happy coding!
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