Get Network Prefix Length in Java

import java.net.InterfaceAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
// w w w.  j  a  v a  2s  . c o  m
public class Main {
  public static void main(String[] args) throws Exception {
    Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces();
    while (en.hasMoreElements()) {
      NetworkInterface ni = en.nextElement();
      System.out.println(" Display Name = " + ni.getDisplayName());

      List<InterfaceAddress> list = ni.getInterfaceAddresses();
      Iterator<InterfaceAddress> it = list.iterator();

      while (it.hasNext()) {
        InterfaceAddress ia = it.next();
        System.out.println(" Network prefix length = " + ia.getNetworkPrefixLength());
      }
    }
  }
}