1. AntiPatterns & CodeSmells
Common practices to improve code quality

2. Anti patterns
Counterpart to design patterns

3. What is an Anti pattern?
 The result of a developer not knowing any better, not
having sufficient knowledge or experience in solving
a particular type of problem.
 Or a developer has applied a perfectly good pattern
in the wrong context.

4. The Blob
 Also known as: «The God Class»
 Root Causes: Sloth, Haste
 Anecdotal Evidence: “This is the class that is really
the heart of our architecture:”
 Refactoring: Refactoring of Responsibilities

5. Lava Flow
 Also known as: Dead Code
 Root Causes: Greed, Sloth
 Anecdotal Evidence: “Oh that! Well Ray and Emil (they’re no
longer with the company) wrote that routine back when Jim (who left
last month) was trying a workaround for Irene’s input processing
code (she’s in another department now, too). I don’t think it’s used
anywhere now, but I’m not really sure.
 Refactoring: Architectural Configuration
Management

6. Golden Hammer
 Definition: A Golden Hammer is a familiar
technology or concept applied obsessively to many
software problems.
 Root Causes: Ignorance, Pride, Narrow-
Mindedness
 Anecdotal Evidence: “I have a hammer and
everything is a nail.”, “Our database is our
architecture.”
 Refactoring: Expand your horizons

7. Code smells
Give you a hint when something is wrong

8. What is a Code smell?
 If it stinks, change it.
 Helps you to spot a code portion which should be
refactored.
 Tries to explain not only you should refactor, but why
you should do so.

9. Duplicated code
Definition
 (Nearly) the same code
structure in more than
one place
Refactorings
 Extract Method
 Extract Class
 Pull Up Field
 Template Method

10. Shotgun Surgery
Definition
 Every time you make a
kind of change, you
have to make a lot of
little changes to a lot of
different classes
Refactorings
 Move Method
 Move Field
 Inline Class

11. Switch Statements
Definition
 The problem with switch
statements is essentially
that of duplication.
 Often you find the same
switch statement over
and over again.
 If you add a new clause
to the switch, you have
to find all the other
switches and change
them.
Refactorings
 Replace with Strategy
 Replace with State
 Replace Conditional
with Polymorphism

12. Data class
Definition
 Class that has only
fields, no methods
operating on these
fields.
 Contains fields which
are manipulated from
other classes
Refactorings
 Encapsulate Fields
 Encapsulate Collection
 Move Method
 Extract Method

13. Overview
 Bad Smells in Code
 Bad Smells in Code
 Duplicated Code
 Long Method
 Large Class
 Long Parameter List
 Divergent Change
 Shotgun Surgery
 Feature Envy
 Data Clumps
 Primitive Obsession
 Switch Statements
 Parallel Inheritance Hierarchies
 Lazy Class
 Speculative Generality
 Temporary Field
 Message Chains
 Middle Man
 Inappropriate Intimacy
 Alternative Classes with Different Interfaces
 Incomplete Library Class
 Data Class
 Refused Bequest
 Comments
 Development AntiPatterns
 The Blob
 Continuous Obsolescence
 Lava Flow
 Ambiguous Viewpoint
 Functional Decomposition
 Poltergeists
 Boat Anchor
 Golden Hammer
 Dead End
 Spaghetti Code
 Input Kludge
 Walking through a Minefield
 Cut-And-Paste Programming
 Mushroom Management

14. Refactoring – Improving the design of
existing code
 Martin Fowler (1963)
 Author and international speaker
on software development,
specialized in OO design.
 Kent Beck (1961)
 Software engineer and the
creator of Extreme Programming
and TDD software development
methodologies.
 Publication date: 28 Jun
1999
 ISBN-13: 978-0201485677

15. Resources
www.SourceMaking.com