1. Code Smells: Ooh, Ooh, That Smell !
Amandeep Batra
October 2016

2. Agenda
ØWhat are Code Smells?
ØWhy do they occur?
ØWhat is the Impact?
ØCode Smells
ØReal World Example Code

3. Interesting Bay Area Conversations
ØWe’d better not touch this code. Last time we did…
ØI thought we had a test for this...
ØIt always worked, who touched it?
ØWhere is e-mail about this issue?
ØAssigning this to X who will come back on next Thursday
ØJust add a TODO comment
ØLets put a Hack for now
ØLets create a SIM for Refactoring for now
ØLets Deliver Results for now

4. What are Code Smells?
ØCode Smells are anti-pattern which represents hazards in the code
ØIt is a design that duplicates, complicates or tightly couples code
ØAnother similar term we commonly use is called Technical Debt
ØRecognizing hazards in the code is the first step in improving code

5. Why do they occur?
ØConsciously: when we defer
ØUnconsciously: when we don’t even

6. What is the impact?

7. Lost Intent

8. Lost Intent Example

9. Inefficient Naming

10. Inefficient Naming
In a Game, we need to write a function
on direction the soldier is facing
getDrctn() : Shorteing a vowel is bad
getDir() : Misleading
getDirection() : Right

11. Duplicated Code
• DRY: Don’t Repeat Yourself

12. Duplicated Code
• DRY: Don’t Repeat Yourself

13. Deodorant Comment
ØIf you write intention revealing code then comments are unnecessary

14. Long Method
ØLike a very large burger, too hard to digest
Shorter composed methods are
- More Readable
- Provide greater opportunity for code sharing, less duplication
- Easier to test

15. Large Class
ØLike people, classes suffer when they take too many responsibilities

16. ØAll of us would dispose of a pet goldfish if it met an unhappy end. Yet
how many of us dispose of code that is no longer being used?
ØLeads to
• Increased Complexity
• Accidental Changes
• More Dead Code
Dead Code

17. Oddball Solution
ØWhen a problem is solved one way throughout a system and same is
solved another way in same system

18. Oddball Solution

19. Primitive Obsession
ØCode that exhibits primitive obsession tends to rely on:
• primitives (like integers or strings)
• low-level methods
• classes that don't easily solve problems
ØCode that suffers from this smell fails to leverage higher level
abstractions.
if (someString.indexOf("substring") != -1)
Instead of
if (someString.contains("substring"))

20. Speculative Generality
ØOh, I think we will need the ability to do that someday" and thus
want all sorts of hooks and special cases to handle things that aren't
required

21. Combinatorial Explosion
ØWhen new combinations of data or behavior further bloat an already
bloated design

22. Combinatorial Explosion
ØList readOnlySortedList = new ReadOnlyList( new SortedList( new
ArrayList(...) ) );

23. Black Sheep
ØA black sheep is a family member that doesn't fit in so well, it could
be a sub-class or a method in a class

24. Black Sheep

25. Feature Envy
ØResponsibilities of performing a job is in wrong place

26. Feature Envy

27. Refused Bequest
ØSubclasses gets to inherit the methods and data of their parents. But what if
they don't want or need what they are given?
public abstract class AbstractCollection…
public abstract void add(Object element);
public class Map extends AbstractCollection…
// Do nothing because user must input key and value
public void add(Object element) { }

28. Other Smells
ØLong Parameterized List : The more the parameters, difficult is to
read, prefer an Object
ØIndecent Exposure : Beware of classes that unnecessarily expose
their internals. Aggressively refactor classes to minimize their public
surface.

29. Example Code
ØLet’s find out some code smells here

30. Some Tips
Ø“Always code as if person who will maintain your
code is a maniac serial killer who knows where you
live”
Ø “Always leave the code in better state than it is
today”

31. Resources
ØRefactoring to Patterns Book
ØCoding Horror Blog

32. Q&A

33. Thanks !