This is a 45 minute talk I've given a couple of times. Heavily based on the book Clean Code.

2. Fredrik Wendt

3. Clean Code
what, why, how

4. http://blog.xebia.com/2009/01/clean-code-vs-implementation-patterns/

5. Disclaimer
Correlation between
Clean code and success?

6. How is it even possible
for code to be this bad?

7. Exhibits
• Hudson class is 3900+
LOC
• Hudson class is untestable
Singleton
• Constructor calls a method
that gets the singleton
instance and calls a method
on the instance.
• Hudson extends Node, but
Node calls methods defined
in Hudson

8. WTF!
So why care – Jenkins is great?

10. ”Smart” vs Professional
• Smart • Professional
● Great coding skills ● Readable code
● Writes advanced code ● Maintainable code
● String r; // lowercase url ● 'Clarity is king'
● String lowerCaseUrl
OfCurrentPage;
http://www.slideshare.net/JandV/clean-code-summary

11. What is Clean Code?

12. int d; // elapsed time in days

13. int d; // elapsed time in days
int elapsedTimeInDays;

14. int d; // elapsed time in days
int elapsedTimeInDays;
int daysSinceCreation;

15. int d; // elapsed time in days
int elapsedTimeInDays;
int daysSinceCreation;
int fileAgeInDays;

16. public List<int[]> getThem() {
List<int[]> list1 = new ArrayList<int[]>();
for (int[] x : theList)
if (x[0] == 4)
list1.add(x);
return list1;
}

17. public List<int[]> getThem() {
List<int[]> list1 = new ArrayList<int[]>();
for (int[] cell : gameBoard)
if (cell[STATUS_VALUE] == FLAGGED)
list1.add(cell);
return list1;
}

18. public List<int[]> getFlaggedCells() {
List<int[]> flaggedCells = new ArrayList<int[]>();
for (int[] cell : gameBoard)
if (cell[STATUS_VALUE] == FLAGGED)
flaggedCells.add(cell);
return flaggedCells;
}

19. public List<Cell> getFlaggedCells() {
List<Cell> flaggedCells = new ArrayList<Cell>();
for (Cell cell : gameBoard)
if (cell.isFlagged())
flaggedCells.add(cell);
return flaggedCells;
}

20. Clean code always
looks like it was written by
someone who cares

21. Clean code always
looks like it was wrtten by
somone who craes

22. Readable
Maintainable
Changeable

23. Agile Manifesto
Individuals and interactions
over processes and tools
Working software
over comprehensive documentation
Customer collaboration
over contract negotiation
Responding to change
over following a plan

25. Readable?

26. ~ 90% of your time is reading
What if you'd
ddouble write-time
and thereby
cut read-time
by half?

27. public class Part {
private String m_dsc; // The textual description
void setName(String name) {
m_dsc = name;
}
}
public class Part {
private String description;
void setDescription(String description) {
this.description = description;
}
}

28. Still, why bother?

29. Code is written for humans!

30. Why?
Who's the main recipient of the code we write – a computer, an
end user or a programmer?
The primary user of source
code is a programmer, perhaps
● your Customer
● your Colleague
● You

31. How should I write code?

32. DRY - Don't Repeat Yourself
YAGNI - You Ain't Gonna Need It

33. small

34. Meaningful Names
• Intention-Revealing • JobQueue
• Pronounceable • Words from the domain
• Avoid Encoding
• Comments
• Classes • Formatting!
• Methods

35. Law of Demeter
More formally, the Law of Demeter
for functions requires that
a method M of an object O
may only invoke the methods of
the following kinds of objects:
1. O itself
2. M's parameters
3. any objects created/instantiated within M
4. O's direct component objects
5. a variable, accessible by O, in the scope of M

36. Dog's Legs
public class CareTaker {
private Dog dog;
...
public void walkTheDog(){
dog.walk();
dog.stop(); // tree or grass etc
dog.doYourThing();
...
}
}

37. Dog's Legs
public class CareTaker {
private Dog dog;
...
public void walkTheDog(){
for (Leg leg : dog.getLegs())
leg.move();
for (Leg leg : dog.getLegs())
leg.stopMoving();
dog.brain.urinationCenter.releaseUrge();
...
}
}

38. Don't talk to strangers
http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/paper-boy/

39. Law of Demeter
public class PaperBoy {
private Wallet myWallet;
...
public void chargeCustomer(Customer customer) {
Wallet wallet = customer.getWallet();
Collection<Bill> bills = wallet.getBills();
Collection<Bill> payment = extract(5, bills);
myWallet.add(payment); // or bills?
}
}

40. Law of Demeter
public class PaperBoy {
private Wallet myWallet;
...
public void chargeCustomer(Customer customer) {
Collection<Bill> payment = customer.getPayment(5);
myWallet.add(payment);
}
}

41. Single Responsibility
1
small

43. Boy Scout Rule
Leave the campground cleaner than you found it.

44. Hur mäter man Clean Code?
Eller kodkvalitet?

45. Can you measure Clean Code?
Or code quality?

46. WTFs / minute
The only valid
measurement of
code quality

47. Summary
Source code vs machine code
Write with the audience in minde
Smart vs Professional
Code quality and retrospectives
Code Review (wtf!) vs pair programming

48. Legacy Code
Code with no tests

49. What about the code that's
already in my backpack?
• Get the old man on track
– make the code testable
(and tested)
• Fix bugs brought out in
daylight by the tests
• ”Make it right”

50. What about the code that's
already in my backpack?
• Get the old man on track
– make the code testable
(and tested)
• Fix bugs brought out in
daylight by the tests
• ”Make it right” – refactor!

51. Code without tests ...
• is legacy code
• is not refactored
• unlikely to be changed by
someone other than the
person who wrote it (the
past few days)
• is heavy load/back pack