The document discusses the importance of refactoring in software design to improve quality and reduce costs associated with poor design, which amounts to billions annually. It highlights the concept of 'code smells'—indicators of potential refactoring needs—and the principles of good software design, including abstraction and encapsulation. Additionally, it presents various tools and techniques for detecting design smells and refactoring legacy code.

1. Refactoring for
Software Design Smells
Ganesh Samarthyam
ganesh@codeops.tech

2. –Craig Larman
"The critical design tool for software development
is a mind well educated in design principles"

3. Warm-up question #1
What does this tool
visualize?

4. Warm-up question #2
Who coined
the term
“code smell”?
Hint: He also
originated the
terms TDD
and XP

5. Warm-up question #3
Who wrote the foreword for
our book?

6. Why care about design quality and
design principles?

7. Poor software quality costs
more than $150 billion per year
in U.S. and greater than $500
billion per year worldwide
- Capers Jones
Why care? Reason #1

8. * h$p://sqgne.org/presenta2ons/2012-13/Jones-Sep-2012.pdf
0
20
40
60
80
100
120
IBM
Corporta+on
(MVS)
SPR Corpora+on
(Client Studies)
TRW
Corpora+on
MITRE
Corpora+on
Nippon Electric
Corp
Percentage Contribu+on
Industry Data on Defect Origins
Adminstra+ve Errors
Documenta+on Errors
Bad Fixes
Coding Errors
Design Errors
Requirements Errors
Up to 64% of soNware defects can be traced back
to errors in soNware design in enterprise soNware!
Why care? Reason #1

9. Source: Consortium of IT Software Quality (CISQ), Bill Curtis, Architecturally Complex Defects, 2012

10. “The problem with quick and dirty...is that dirty
remains long after quick has been forgotten”
Steve C McConnell

11. Why care? Reason #3
“Technical debt is the debt that accrues
when you knowingly or unknowingly make
wrong or non-optimal design decisions”

12. Why care? Reason #3
Reference: Zen and the art of software quality – Jim Highsmith Agile 2009 conference

14. Recent Korean
translation of
the book

15. "... a delightful, engaging, actionable read... you have
in your hand a veritable field guide of smells... one
of the more interesting and complex expositions of
software smells you will ever find..."
- From the foreword by Grady Booch (IBM Fellow and Chief Scientist for
Software Engineering, IBM Research)

16. "We thought we were just programming on an airplane”
- Kent Beck
Why care? Reason #2

17. "This is a good book about ‘Design Smells’ – actually
a great book – nicely organized - clearly written with
plenty of examples and a fair sprinkling of
anecdotes."
- Will Tracz (Principal Research Scientist & Fellow,
Lockheed Martin)
(review in ACM SIGSOFT Software Engineering
Notes)

18. Fundamental principles in software design
Principles*
Abstrac/on*
Encapsula/on*
Modulariza/on*
Hierarchy*

19. Effective design: Java parallel streams
❖ Applies the principles of abstraction and encapsulation
effectively to significantly simplify concurrent
programming
Parallel code
Serial code

20. Parallel streams: example
import java.util.stream.LongStream;
class PrimeNumbers {
private static boolean isPrime(long val) {
for(long i = 2; i <= val/2; i++) {
if((val % i) == 0) {
return false;
}
}
return true;
}
public static void main(String []args) {
long numOfPrimes = LongStream.rangeClosed(2, 50_000)
.parallel()
.filter(PrimeNumbers::isPrime)
.count();
System.out.println(numOfPrimes);
}
}

21. long numOfPrimes = LongStream.rangeClosed(2, 100_000)
.filter(PrimeNumbers::isPrime)
.count();
System.out.println(numOfPrimes);
Prints 9592
2.510 seconds

22. Parallel code
Serial code
Let’s flip the switch by
calling parallel() function

23. long numOfPrimes = LongStream.rangeClosed(2, 100_000)
.parallel()
.filter(PrimeNumbers::isPrime)
.count();
System.out.println(numOfPrimes);
Prints 9592
1.235 seconds

24. Proactive application: enabling techniques

25. Reactive application: smells

26. What are smells?
“Smells'are'certain'structures'
in'the'code'that'suggest'
(some4mes'they'scream'for)'
the'possibility'of'refactoring.”''

27. What is refactoring?
Refactoring (noun): a change
made to the internal structure of
software to make it easier to
understand and cheaper to
modify without changing its
observable behavior
Refactor (verb): to restructure
software by applying a series
of refactorings without
changing its observable
behavior

28. Design smells: example #1

29. Discussion example

30. Design smells: example #2

31. Discussion example

32. Design smells: example #3

33. Discussion example
// using java.util.Date
Date today = new Date();
System.out.println(today);
$ java DateUse
Wed Dec 02 17:17:08 IST 2015
Why should we get the
time and timezone details
if I only want a date? Can
I get rid of these parts?
No!

34. So what!
Date today = new Date();
System.out.println(today);
Date todayAgain = new Date();
System.out.println(todayAgain);
System.out.println(today.compareTo(todayAgain) == 0);
Thu Mar 17 13:21:55 IST 2016
Thu Mar 17 13:21:55 IST 2016
false
What is going
on here?

35. Refactoring for Date
Replace inheritance
with delegation

36. Joda API
Stephen Colebourne

37. java.time package!
Date, Calendar, and TimeZone
Java 8 replaces
these types

38. Refactored solution
LocalDate today = LocalDate.now();
System.out.println(today);
LocalDate todayAgain = LocalDate.now();
System.out.println(todayAgain);
System.out.println(today.compareTo(todayAgain) == 0);
2016-03-17
2016-03-17
true
Works fine
now!

39. Refactored example …
You can use only date,
time, or even timezone,
and combine them as
needed!
LocalDate today = LocalDate.now();
System.out.println(today);
LocalTime now = LocalTime.now();
System.out.println(now);
ZoneId id = ZoneId.of("Asia/Tokyo");
System.out.println(id);
LocalDateTime todayAndNow = LocalDateTime.now();
System.out.println(todayAndNow);
ZonedDateTime todayAndNowInTokyo = ZonedDateTime.now(ZoneId.of("Asia/Tokyo"));
System.out.println(todayAndNowInTokyo);
2016-03-17
13:28:06.927
Asia/Tokyo
2016-03-17T13:28:06.928
2016-03-17T16:58:06.929+09:00[Asia/Tokyo]

40. More classes in Date/Time API

41. What’s that smell?

42. Liskov’s Substitution Principle (LSP)
It#should#be#possible#to#replace#
objects#of#supertype#with#
objects#of#subtypes#without#
altering#the#desired#behavior#of#
the#program#
Barbara#Liskov#

43. Refactoring
Replace inheritance
with delegation

44. What’s that smell?
switch'(transferType)'{'
case'DataBuffer.TYPE_BYTE:'
byte'bdata[]'='(byte[])inData;'
pixel'='bdata[0]'&'0xff;'
length'='bdata.length;'
break;'
case'DataBuffer.TYPE_USHORT:'
short'sdata[]'='(short[])inData;'
pixel'='sdata[0]'&'0xffff;'
length'='sdata.length;'
break;'
case'DataBuffer.TYPE_INT:'
int'idata[]'='(int[])inData;'
pixel'='idata[0];'
length'='idata.length;'
break;'
default:'
throw' new' UnsupportedOperaQonExcepQon("This' method' has' not' been' "+' "implemented'
for'transferType'"'+'transferType);'
}'

45. Replace conditional with polymorphism
protected(int(transferType;! protected(DataBuffer(dataBuffer;!
pixel(=(dataBuffer.getPixel();(
length(=(dataBuffer.getSize();!
switch((transferType)({(
case(DataBuffer.TYPE_BYTE:(
byte(bdata[](=((byte[])inData;(
pixel(=(bdata[0](&(0xff;(
length(=(bdata.length;(
break;(
case(DataBuffer.TYPE_USHORT:(
short(sdata[](=((short[])inData;(
pixel(=(sdata[0](&(0xffff;(
length(=(sdata.length;(
break;(
case(DataBuffer.TYPE_INT:(
int(idata[](=((int[])inData;(
pixel(=(idata[0];(
length(=(idata.length;(
break;(
default:(
throw( new( UnsupportedOperaRonExcepRon("This( method(
has( not( been( "+( "implemented( for( transferType( "( +(
transferType);(
}!

46. Refactoring: Practical concerns
“Fear of breaking
working code”
Is management buy-in necessary for refactoring?
How to refactor code in legacy projects (no automated
tests, difficulty in understanding, lack of motivation, …)?
Where do I have time
for refactoring?

47. Tool driven approach for design
quality

48. Comprehension tools
STAN
http://stan4j.com

49. Comprehension tools
Code City
http://www.inf.usi.ch/phd/wettel/codecity.html

50. Comprehension tools
Imagix 4D
http://www.imagix.com

51. Smell detection tools
Infusion
www.intooitus.com/products/infusion

52. Smell detection tools
Designite
www.designite-tools.com

53. Clone analysers
PMD Copy Paste Detector (CPD)
http://pmd.sourceforge.net/pmd-4.3.0/cpd.html

54. Metric tools
Understand
https://scitools.com

55. Technical debt quantification/visualization tools
Sonarqube
http://www.sonarqube.org

56. Refactoring tools
ReSharper
https://www.jetbrains.com/resharper/features/

57. Source: Neal Ford, Emergent Design: https://dl.dropbox.com/u/6806810/Emergent_Design%28Neal_Ford%29.pdf

58. http://xpconference.in/2016/

59. Tangles in
JDK

62. Refactoring for Software Architecture Smells
Ganesh Samarthyam, Tushar Sharma and Girish Suryanarayana
http://www.softrefactoring.com/

63. Meetups
h"p://www.meetup.com/JavaScript-Meetup-Bangalore/
h"p://www.meetup.com/Container-Developers-Meetup-Bangalore/
h"p://www.meetup.com/So>ware-Cra>smanship-Bangalore-Meetup/
h"p://www.meetup.com/Core-Java-Meetup-Bangalore/
h"ps://www.meetup.com/Mobile-App-Developers-Bangalore-Meetup/
h"p://www.meetup.com/CloudOps-Meetup-Bangalore/
h"p://www.meetup.com/Bangalore-SDN-IoT-NetworkVirtualizaIon-Enthusiasts/
h"p://www.meetup.com/So>wareArchitectsBangalore/

64. ganesh@codeops.tech @GSamarthyam
www.codeops.tech slideshare.net/sgganesh
+91 98801 64463 bit.ly/ganeshsg