Presentation about code refactoring and importance of code quality

1. Code Refactoring
Milan Vukoje
www.vukoje.net

2. Soprex
• SkfOffice2
• SkfOffice3
• Big5
• Quality oriented
• We are hiring…

3. Agenda
• Why is (clean) code important?
• Refactoring (definition and samples)
• Tools
• When to and when not to refactor?
• Summary

4. Is code important?
• Is construction relatively mechanical process?
• Only activity that’s guaranteed to be done
• 50-65% of overall effort
• 50-75% of overall errors

5. Coding Horror
• Stress
• Fear
• Cargo cult programming
• “Just in case” coding
• Unusual software bugs (Heisenbug
, Mandelbug, Schroedinbug… )

6. Code Example

7. Technical Debt
– If you can get today's work done today, but you do it
in such a way that you can't possibly get tomorrow's
work done tomorrow, then you lose. – Kent Beck
• When software organization chooses a design or
construction approach that's expedient in the short
term but that increases complexity and is more
costly in the long term.
• Unintentional and intentional debt

8. Refactoring
• Refactoring - a change made to the internal structure of software to
make it easier to understand and cheaper to modify without changing
its observable behavior.
• Set of rules and techniques for enhancing code while reducing
chances for error
• Refactoring: Improving the Design of Existing Code --Martin
Fowler

9. Composing Methods
1. Extract Method
void printOwing(double amount) {
printBanner();
//print details
System.out.println ("name:" + _name);
System.out.println ("amount" + amount);
}
void printOwing(double amount) {
printBanner();
printDetails(amount);
}
void printDetails (double amount) {
System.out.println ("name:" + _name);
System.out.println ("amount" + amount);
}

10. Composing Methods
2. Inline Method
int getRating() {
return (moreThanFiveLateDeliveries()) ? 2 : 1;
}
boolean moreThanFiveLateDeliveries() {
return _numberOfLateDeliveries > 5;
}
int getRating() {
return (_numberOfLateDeliveries > 5) ? 2 : 1;
}

11. Managing temps
1. Inline Temp
double basePrice = anOrder.basePrice();
return (basePrice > 1000)
return (anOrder.basePrice() > 1000)

12. Managing temps
2. Replace Temp with Query
double basePrice = _quantity * _itemPrice;
if (basePrice > 1000)
return basePrice * 0.95;
else
return basePrice * 0.98;
if (basePrice() > 1000)
return basePrice() * 0.95;
else
return basePrice() * 0.98;
...
double basePrice() {
return _quantity * _itemPrice;
}

13. Managing temps
3. Introduce Explaining Variable
if ( (platform.toUpperCase().indexOf("MAC") > -1) &&
(browser.toUpperCase().indexOf("IE") > -1) &&
wasInitialized() && resize > 0 )
{
// do something
}
final boolean isMacOs = platform.toUpperCase().indexOf("MAC") > -1;
final boolean isIEBrowser = browser.toUpperCase().indexOf("IE") > -1;
final boolean wasResized = resize > 0;
if (isMacOs && isIEBrowser && wasInitialized() && wasResized) {
// do something
}

14. Simplifying conditionals
1. Decompose Conditional
if (date.before (SUMMER_START) || date.after(SUMMER_END))
charge = quantity * _winterRate + _winterServiceCharge;
else charge = quantity * _summerRate;
if (notSummer(date))
charge = winterCharge(quantity);
else charge = summerCharge (quantity);

15. Simplifying conditionals
2. Consolidate Duplicate Fragments
if (isSpecialDeal()) {
total = price * 0.95;
send();
}
else {
total = price * 0.98;
send();
}
if (isSpecialDeal())
total = price * 0.95;
else
total = price * 0.98;
send();

16. Simplifying conditionals
3. Consolidate Conditional Expression
double disabilityAmount() {
if (_seniority < 2) return 0;
if (_monthsDisabled > 12) return 0;
if (_isPartTime) return 0;
// compute the disability amount
double disabilityAmount() {
if (isNotEligableForDisability()) return 0;
// compute the disability amount

17. Moving Features between objects
• Replace Method with Method Object
• Extract/Inline Class
• Pull Up/Down Field/Method
• Extract Subclass/ Superclass/Interface
• Collapse Hierarchy

18. Benefits
• Less code
– less bugs
• Readable business logic
– better business domain understanding
• Self explaining code
– Less documentation and faster changes
• Better design
– Higher encapsulation and reusability
– Cleaner concepts and structure

19. Visual Studio 2008

20. Need for refactoring
• Why change something that works?
– We want programs that are easy to read, that have all logic
specified in one and only one place, that do not allow changes to
endanger existing behavior, and that allow conditional logic to be
expressed as simply as possible. --Kent Beck
• Micro design - clear API and logical structures
• Code evolution - Embracing change
• Avoiding coding horror by managing complexity
• Agile methods (XP, TDD, Scrum)

21. When Should You Refactor?
• Not having enough time usually is a sign that you need to do some
refactoring. – Martin Fowler
• Refactor all the time in little steps
• Refactor when you:
– add function
– fix a bug
– do a code review
• Refactoring and Unit Tests?

22. Code smells
• Duplicated Code
• Long Method
• Large Class
• Switch Statements
• Lazy Class
• Speculative Generality
• Temporary Field
• Message Chains
• …

23. When you shouldn’t refactor?
Avoid refactoring:
• Databases
• Published interfaces
• Code is so full of bugs that you cannot stabilize it
• When you are very close to a deadline
• When you are not sure
• Don’t overdo it (no silver bullet)
– Perfect is the enemy of good, and good is what we want

24. Performance and Refactoring
• Performance optimization = obscure code
• Optimized for humans = slower code but
easier tuning
• 10% optimized code is usually enough

25. What Do I Tell My Manager?
• If the manager is quality oriented, then the thing to
stress is the quality aspects.
• Tons of studies show that technical reviews are an
important way to reduce bugs and thus speed up
development.
• Don't tell!?

26. Summary
1. Programming is hard and complex
2. (Clean) Code is very important
3. Refactoring can help you achieve clean code
and better design.
4. Refactoring should be used wisely
1. Don’t over do it (no silver bullet)
2. Know when not to refactor
3. Changes must not cause new bugs

27. Questions?
Milan Vukoje
www.vukoje.net
vukoje@gmail.com

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