code: public static Integer getSegmentPrefixLength(int bitsPerSegment, Integer prefixLength, int segmentIndex) {
  		if(prefixLength != null) {
  			return getPrefixedSegmentPrefixLength(bitsPerSegment, prefixLength, segmentIndex);
  		}
  		return null;
  	}
docs: Across an address prefixes are:
  IPv6: (null):...:(null):(1 to 16):(0):...:(0)
  or IPv4: ...(null).(1 to 8).(0)...