We appear to have a regression in jdk7/tl/jdk since this push:
  http://hg.openjdk.java.net/jdk7/tl/jdk/rev/887e525597f8

The problem is that NetworkInterface.getInetAddresses enumerates IPv6 addresses when java.net.preferIPv4Stack=true.

Try the following with jdk7-b98 and compare with a build of jdk7/tl/jdk. The latter enumerates IPv6 addresses, a nasty regression.

import java.net.*;
import java.util.*;

public class Test {
    public static void main(String[] args) throws Exception {
            Enumeration<NetworkInterface> nifs = NetworkInterface.getNetworkInterfaces();
            while (nifs.hasMoreElements()) {
                NetworkInterface nif = nifs.nextElement();
                Enumeration<InetAddress> addrs = nif.getInetAddresses();
                while (addrs.hasMoreElements()) {
                    System.out.println(addrs.nextElement().getHostAddress());
                }
            }
        
    }
}