Clean Code

Clean Code

Presentation of the Uncle Bob's Book.

Thursday, December 1, 11 1

The Speaker
• Brice Argenson
– Full Professor in Java and Web Technologies
• Professional Experiences :
– Bug Out PC – Audaxis
– ADF – Groupe Open
– Adullact – Atos Worldline
– Webpulser – Xebia IT
• Certifications :
– SCJP 6 – MCP – Exam 70-316
– SCWCD 5

brice.argenson@supinfo.com @bargenson

Agenda

• Software Craftsmanship

• Why Clean Code ?

• Tips & Tricks to write Clean Code

• References


What is that ?

SOFTWARE CRAFTSMANSHIP


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6


Bad Code VS. Clean Code

WHY CLEAN CODE ?


Bad Code
• Bad Code killed some companies
– Rushed the product to market
– More and more features
– Worse and worse code
– Code unmanageable

• We all wrote bad code
– Trying to go fast ?
– We were in a rush ?
– We’ll clean it up later…


The Cost of Bad Code
• Do you have been slowed down by messy code ?

• More & more mess è Less & less productivity

• When productivity became terrible è Redesign

• And again…
• And again…


Whose Fault ?
• The customer ?
– The requirements change too much ?
• The managers ?
– The deadlines are too short ?
• It is mainly the developer fault !
– The others look to us for the information they need
– The doctor knows more than the patient about the risks
[…]

• Be professionals !


What is Clean Code ?
• What is Clean Code for you ?
– It is working ?
– It is efficient ?
– It is short ?

• Clean Code is easy to read !

• We are authors !


What is Clean Code ?

• The Boy Scout Rule :
– Leave the campground cleaner than you found it.

• Refactor your code !

• Write tests !
– Test Driven Development


How to write Clean Code ?

GET YOUR HANDS DIRTY !


Meaningful Names
• What is the purpose of this code ?


Meaningful Names
• And what do you think of this code ?


Meaningful Names
• Use Intention-Revealing Names


Meaningful Names

• What about Hungarian Notation ?


Meaningful Names

• What if one day we change the type ?

• Hungarian Notation make it harder to change the
name or type of a variable, function or class


Meaningful Names
• What about Member Prefixes ?
– Example: m_firstName

• Classes and functions should be small enough that
you don’t need them

• IDE highlights or colorizes members !

• Prefixes become unseen clutter


Functions
• What do you think about this method ?
– FitNesse - commit 3bec390e6f

• And now ?
– FitNesse - commit 7491001db7

• What has changed ?


Functions
• Small !
– Not bigger than a screen full
• Correct in the eighties (24 x 80)
– Should be transparently obvious
– Indent level should not be greater than one or two
• Do one thing !
– Your function is divided into section ?
• You can divide it !
• The Stepdown Rule !
– We want the code to read like a top-down narrative


Functions
• Function arguments ?
– Niladic
• The ideal number
– Monadic
• A good number
– Dyadic
• A good number
– Triadic
• Should be avoided
– Polyadic
• Do you need to wrap the arguments into a new type ?


Error Handling

• What do you think about this code ?


Error Handling

• Prefer exceptions to returning error codes


Error Handling

• And what do you think about this code ?


Error Handling

• For you what is the most common exception ?
– NPE !

• How to avoid it ?

28


Error Handling


29


Error Handling

• Don’t return Null !

30


Error Handling


31


Error Handling

• How to make code look like that ?

• Special Case object !

32


Side Effects
• Consider the following class :

33


Side Effects

• Consider the following code :

• Do you see the problem ?

34


Side Effects

• To protect the internals of a Period instance from
this sort of attack:

– You must make defensive copy of each mutable
parameter to the constructor !

35


Side Effects

• Inheritance is a powerful way to achieve code
reuse
– But not always the best !

• Inheritance from ordinary concrete classes across
package boundaries is dangerous !

• Unlike method invocation, inheritance violates
encapsulation

36


Side Effects

37


Side Effects

• What this code display ?

38


Side Effects

39


Side Effects

40


Side Effects
• Design of the InstrumentedSet is extremely
flexible :
– Implement the Set interface
– Receive an argument also of type Set

• With inheritance, we could work only with HashSet

• With composition, we can work with any Set
implementation !

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Side Effects

• Favor composition over inheritance !

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Do you want to read more about the subject ?

REFERENCES

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Books

Clean Code
A Handbook of Agile Software Craftsmanship

Robert C. Martin (aka. Uncle Bob)

Prentice Hall editions

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Books

Effective Java
Second Edition

Joshua Bloch

Addison Wesley editions

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Links
• Sign the Manifesto
– http://manifesto.softwarecraftsmanship.org

• Software Craftsmanship en pratique - Xebia
– http://blog.xebia.fr/2011/01/31/software-craftsmanship-
en-pratique/

• The Clean Coder - Uncle Bob blog
– http://thecleancoder.blogspot.com/

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Clean Code

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