Refactoring
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This document discusses refactoring code to improve its structure and design without changing its external behavior. Refactoring involves applying small, incremental changes through techniques like extracting methods, replacing conditionals, and parameterizing methods. It improves code quality by making it more readable, reusable, maintainable and less error-prone. The key is to refactor in small steps through practices like testing and code reviews to pay off technical debt over time.
![Replace Exception with Testdouble getValueForPeriod (int period) { try { return values[period]; } catch (ArrayIndexOutOfBoundsException e) { return 0; }}double getValueForPeriod (int period) { return period >= values.length ? 0 : values[period];}](https://image.slidesharecdn.com/part3-refactoring-110828072917-phpapp01/85/Refactoring-26-320.jpg)
Refactoring
- 2. Do You Know Your Code?
- 3. Developer Golden RuleAny fool can write code that a computer can understand
- 4. Good Developer Golden RuleAny fool can write code that a computer can understandGood programmers write code that humans can understand
- 5. Why Fix What is Not Broken?
- 6. If the Code is Hard to UnderstandHard to maintainHard to improveHard to work with evolutionary designMore expensive
- 7. What is Refactoring?A series of small steps, each of which changes the program’s internal structure without changing its external behavior - Martin FowlerVerify no change in external behavior byTestingUsing the right tool (IDE)Formal code analysis by toolCode review or pair programmingBeing very, very careful
- 8. Prerequisites for SuccessSafety netEverybody agreed “Collective code ownership”Common understanding of refactoring methodsSupportive environmentPowerful IDE
- 9. Refactoring CycleFind smellSelect refactoringApply refactoringRun all tests
- 10. 3 Ways to Start
- 11. Find Something to Improve
- 13. Find Smell
- 14. How to Find Smell
- 15. Smells
- 16. Main GoalsOrganizing dataComposing methodsMaking methods calls simplerMoving features between objectsSimplifying conditional expressionDealing with generalizations
- 17. Operations Associated with RefactoringReplaceExtractMoveChangeIntroduceRemovePullConsolidatePushInlineAdd
- 18. When to Refactor?When add new functionalityRefactor existing code until you understand itRefactor the design to make it simple to addWhen try to find bugsRefactor to understand the codeDuring code reviewsImmediate effect of code reviewAllows for higher level suggestions
- 19. Key Elementsof RefactoringSimplifying complex statementsAbstracting common solutions into reusable codeRemoval of duplicate code
- 21. 6 Techniques in Action
- 22. Extract Methodvoid printOwing() {printBanner(); //print detailsSystem.out.println("name: " + _name);System.out.println("amount " + getOutstanding());}void printOwing() {printBanner();printDetails(getOutstanding());}void printDetails (double outstanding) {System.out.println("name: " + name);System.out.println("amount " + outstanding);}
- 24. Decompose Conditionalif (date.before (SUMMER_START) || date.after(SUMMER_END)) { charge = quantity * winterRate+ serviceCharge;} else { charge = quantity * summerRate;}if (notSummer(date)) { charge = winterCharge(quantity);} else { charge = summerCharge (quantity);}
- 25. Replace Error Code with Exceptionboolean withdraw(int amount) { if (amount > balance) return false; else { balance -= amount; return true; }}void withdraw(int amount) throws BalanceException { if (amount > balance) throw new BalanceException(); balance -= amount;}
- 26. Replace Exception with Testdouble getValueForPeriod (int period) { try { return values[period]; } catch (ArrayIndexOutOfBoundsException e) { return 0; }}double getValueForPeriod (int period) { return period >= values.length ? 0 : values[period];}
- 29. No Silver BulletNeeds lots of practiceRequires disciplineContinuous usageLittle steps
- 30. Little steps – huge results
- 31. You Need to Pay Technical Debt
- 32. Refactoring BenefitsMore readable codeEasier maintenanceCode reuseEasier to add new codeImproved designBetter understandingSpeeding knowledgeEasier to testMinimize duplication
- 33. Live Demo
- 34. Questions?
Editor's Notes
- #7: We need to realize that software must be soft: it has to be easy to change because it will change despite our misguided efforts otherwise.
- #10: • Make a small change (a single refactoring)• Run all the tests to ensure everything stillworks• If everything works, move on to the nextrefactoring• If not, fix the problem, or undo the change,so you still have a working system
- #13: Any time you find that you can improve the design of existing codeYou detect a code that smellsAfter static analysis
- #14: Any time you find that you can improve the design of existing codeYou detect a code that smellsAfter static analysis