Awareness of design smells - indicators of common design problems - helps developers or software engineers understand mistakes made while designing and apply design principles for creating high-quality designs. This workshop provides insights gained from performing refactoring in real-world projects to improve refactoring and reduce the time and costs of managing software projects. The workshop also presents insightful anecdotes and case studies drawn from the trenches of real-world projects. By attending this workshop, you will know pragmatic techniques for refactoring design smells to manage technical debt and to create and maintain high-quality software in practice. Contents overview: * Why care about design principles, design quality, or design smells? * Refactoring as the primary means for repaying technical debt * Smells that violate abstraction, encapsulation, modularisation, or hierarchy * Tools and techniques for refactoring

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