code: public static String getMacFor(NetworkInterface iface) throws SocketException, NoMacAddressException
  	{
  		assert (iface != null);
  
  		byte[] hwaddr = iface.getHardwareAddress();
  
  		if (hwaddr == null || hwaddr.length == 0)
  		{
  			throw new NoMacAddressException("Interface " + iface.getName() + " has no physical address specified.");
  		}
  		else
  		{
  			return physicalAddressToString(hwaddr);
  		}
  	}
docs: Given a network interface, determines its mac address
  
  @param iface
  the interface
  
  @return The MAC address formatted in lower-case colon-delimited hexidecimal bytes (aa:ab:ac)
  
  @throws SocketException
  @throws NoMacAddressException
  If the interface doesn't have a mac address