Software Design in Practice (with Java examples)

Software Design in
Practice
Ganesh Samarthyam
Entrepreneur; author; speaker
ganesh@codeops.tech
www.codeops.tech

Discussion Question
Which one of the following is MOST IGNORED aspect in
software development?
❖ Code quality
❖ Software testing
❖ Software design
❖ Programming

"... 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)

Poor software quality costs
more than $150 billion per year
in U.S. and greater than $500
billion per year worldwide
- Capers Jones

Source: Estimating the Principal of an Application's Technical Debt, Bill Curtis, Jay
Sappidi, Alexandra Szynkarski, IEEE Software, Nov.-Dec. 2012.

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

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

For Architects: Design is the Key!

Fundamental Principles in Software Design
Principles*
Abstrac/on*
Encapsula/on*
Modulariza/on*
Hierarchy*

Proactive Application: Enabling Techniques

$ cat limerick.txt
There was a young lady of Niger
Who smiled as she rode on a tiger.
They returned from the ride
With the lady inside
And a smile on the face of the tiger.

$ cat limerick.txt | tr -cs "[:alpha:]" "n" | awk '{print length(), $0}' | sort | uniq
1 a
2 as
2 of
2 on
3 And
3 Who
3 she
3 the
3 was
4 They
4 With
4 face
4 from
4 lady
4 ride
4 rode
5 Niger
5 There
5 smile
5 tiger
5 young
6 inside
6 smiled
8 returned

List<String> lines
= Files.readAllLines(Paths.get("./limerick.txt"), Charset.defaultCharset());
Map<Integer, List<String>> wordGroups
= lines.stream()
.map(line -> line.replaceAll("W", "n").split("n"))
.flatMap(Arrays::stream)
.sorted()
.distinct()
.collect(Collectors.groupingBy(String::length));
wordGroups.forEach( (count, words) -> {
words.forEach(word -> System.out.printf("%d %s %n", count, word));
});
1 a
2 as
2 of
2 on
3 And
3 Who
3 she
3 the
3 was
4 They
4 With
4 face
4 from
4 lady
4 ride
4 rode
5 Niger
5 There
5 smile
5 tiger
5 young
6 inside
6 smiled
8 returned

I really really hate
concurrency problems

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

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

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

Wow! That’s an awesome ﬂip
switch!

Internally, parallel streams make
use of fork-join framework

Discussion Question
What is refactoring?
❖ Needless rework!
❖ Changing internal structure without changing external
behaviour
❖ Changing external quality (scalability, performance, etc)
❖ Fixing hidden or latent defects

What’s that smell?
public'Insets'getBorderInsets(Component'c,'Insets'insets){'
''''''''Insets'margin'='null;'
'''''''''//'Ideally'we'd'have'an'interface'deﬁned'for'classes'which'
''''''''//'support'margins'(to'avoid'this'hackery),'but'we've'
''''''''//'decided'against'it'for'simplicity'
''''''''//'
''''''''if'(c'instanceof'AbstractBuEon)'{'
'''''''''''''''''margin'='((AbstractBuEon)c).getMargin();'
''''''''}'else'if'(c'instanceof'JToolBar)'{'
''''''''''''''''margin'='((JToolBar)c).getMargin();'
''''''''}'else'if'(c'instanceof'JTextComponent)'{'
''''''''''''''''margin'='((JTextComponent)c).getMargin();'
''''''''}'
''''''''//'rest'of'the'code'omiEed'…'

Refactoring
!!!!!!!margin!=!c.getMargin();
!!!!!!!!if!(c!instanceof!AbstractBu8on)!{!
!!!!!!!!!!!!!!!!!margin!=!((AbstractBu8on)c).getMargin();!
!!!!!!!!}!else!if!(c!instanceof!JToolBar)!{!
!!!!!!!!!!!!!!!!margin!=!((JToolBar)c).getMargin();!
!!!!!!!!}!else!if!(c!instanceof!JTextComponent)!{!
!!!!!!!!!!!!!!!!margin!=!((JTextComponent)c).getMargin();!
!!!!!!!!}

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!

So What!
Date today = new Date();
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?

Refactoring for Date
Replace inheritance
with delegation

Joda API
JSR 310: Java Date and Time API
Stephen Colebourne

Refactored Solution
LocalDate today = LocalDate.now();
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!

Refactored Example …
You can use only date,
time, or even timezone,
and combine them as
needed!
LocalDate today = LocalDate.now();
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]

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#

Refactoring
Replace inheritance
with delegation

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);'
}'

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);(
}!

Discussion Question
What is the biggest deterrent to performing refactoring?
❖ Deadlines! (Lack of time and resources)
❖ Fear of breaking the working code
❖ Not able to get management buy-in for refactoring
❖ Lack of technical skills to perform refactoring

Language Features & Refactoring
public static void main(String []file) throws Exception {
// process each file passed as argument
// try opening the file with FileReader
try (FileReader inputFile = new FileReader(file[0])) {
int ch = 0;
while( (ch = inputFile.read()) != -1) {
// ch is of type int - convert it back to char
System.out.print( (char)ch );
}
}
// try-with-resources will automatically release FileReader object
}
public static void main(String []file) throws Exception {
Files.lines(Paths.get(file[0])).forEach(System.out::println);
}
Java 8 lambdas and streams

Structural Analysis for Java (stan4j)

Name the ﬁrst
object
oriented
programming
language

BANGALORE CONTAINER CONFERENCE 2017
Sponsorship
Deck
Apr 07
Bangalore
www.containerconf.in

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

Software Design in Practice (with Java examples)

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