code: public static boolean isValidNetmask(String netmask)
  	{
  		try
  		{
  			return isValidNetmask(InetAddress.getByName(netmask));
  		}
  		catch (UnknownHostException e)
  		{
  			return false;
  		}
  	}
docs: Validates a netmask
  
  @param netmask
  String A netmask to test
  
  @return boolean True if it validates, otherwise false