1. Refactoring hacked
Sebastian Malaca

2. Who am I? Fanatic of the OOP and the Code’s Quality Blogger Speaker
Trainer and consultant
Software Developer at Luxoft
@SebastianMalaca
letstalkaboutjava.blogspot.com
letstalkaboutjava.blogspot.com

3. What's in the Menu? What is Refactoring? Is it worth the effort?
What you should know about Refactoring?
How?
letstalkaboutjava.blogspot.com

4. What is Refactoring?
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5. SMALL CHANGES What is Refactoring?
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6. NO CHANGES!!! SMALL CHANGES What is Refactoring?
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7. READABILITY SMALL CHANGES NO CHANGES!!! What is Refactoring?
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8. Is it worth the effort?
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9. Is it worth the effort? It's expensive -> Small changes -> Habit
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10. Is it worth the effort? It's NOT expensive
Only for big projects -> Success -> Long life
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11. Is it worth the effort? It's NOT expensive NOT only for big projects
Must have in big projects -> Come and go -> no author -> readability
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12. Refactoring vs. Redesign

13. Refactoring vs. Redesign
Readability and Understanding
Atomic changes
Class as a starting point
Ad hoc
Improvements and Extensions
Complex changes
Dependencies
Planning
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14. Stay safe!

15. Stay safe! No tests, no fun!
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16. Stay safe! No tests, no fun! Experimentation or Professionalism?
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17. Stay safe! No tests, no fun! Experimentation or Professionalism?
Doubts vs. Certainty
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18. You have to know when to stop!

19. You have to know when to stop
Refactoring is fun
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20. You have to know when to stop
Refactoring is fun
Refactoring – neverending story
letstalkaboutjava.blogspot.com

21. You have to know when to stop
Refactoring is fun
Refactoring – neverending story
Boundaries and Values
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22. You have to know when to stop
Refactoring is fun
Refactoring – neverending story
Boundaries and Values
Perfection!
letstalkaboutjava.blogspot.com

23. You have to know when to stop
Refactoring is fun
Refactoring – neverending story
Boundaries and Values
Perfection!
Software with the users vs. Ideal software
letstalkaboutjava.blogspot.com

24. You have to know when to stop
Refactoring is fun
Refactoring – neverending story
Boundaries and Values
Perfection!
Software with the users vs. Ideal software
letstalkaboutjava.blogspot.com

25. www.luxoft.com, @SebastianMalaca, letstalkaboutjava.blogspot.com

26. It’s worth to know patterns

27. It’s worth to know patterns
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28. Gimme the name!
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29. Let's take a look at the code!

30. There’s only a small condition…

31. Less dependencies
private TestsRepository testsRepository; private CodeBaseRepository codeBaseRepository; public void apply(ClassCode code, Developer developer) { if (codeBaseRepository.contains(code) && testsRepository.testsExistFor(code)) { startRefactoringOf(code, developer); } }
letstalkaboutjava.blogspot.com

32. Less dependencies
private TestsRepository testsRepository; private CodeBaseRepository codeBaseRepository; public void apply(ClassCode code, Developer developer) { if (codeBaseRepository.contains(code) && testsRepository.testsExistFor(code)) { startRefactoringOf(code, developer); } }
private RefactoringPossiblePredicate refactoringPossiblePredicate; public void apply(ClassCode code) { if (refactoringPossiblePredicate.apply(code)) { startRefactoringOf(code, developer); } }
letstalkaboutjava.blogspot.com

33. The size matters!
private TestsRepository testsRepository; public void apply(ClassCode code, Developer developer) { if (testsRepository.testsExistFor(code) && developer.canModify(code) && (code.isComplex() || code.isUnreadable())) { startRefactoringOf(code); } }
letstalkaboutjava.blogspot.com

34. The size matters! When object knows…
private TestsRepository testsRepository; public void apply(ClassCode code, Developer developer) { if (testsRepository.testsExistFor(code) && developer.canModify(code) && (code.isComplex() || code.isUnreadable())) { startRefactoringOf(code); } }
When object knows…
private TestsRepository testsRepository; public void apply(ClassCode code, Developer developer) { if (testsRepository.testsExistFor(code) && developer.canModify(code) && code.canBeImproved()) { startRefactoringOf(code); } }
letstalkaboutjava.blogspot.com

35. The size matters! Single Responsibility Principle
private TestsRepository testsRepository; public void apply(ClassCode code, Developer developer) { if (testsRepository.testsExistFor(code) && developer.canModify(code) && (code.isComplex() || code.isUnreadable())) { startRefactoringOf(code); } }
private TestsRepository testsRepository; public void apply(ClassCode code, Developer developer) { if (testsRepository.testsExistFor(code) && developer.canModify(code) && code.canBeImproved()) { startRefactoringOf(code); } }
private CanStartRefactoringPredicate canStartRefactoringPredicate; public void apply(ClassCode code, Developer developer) { if (canStartRefactoringPredicate.apply(code, developer)) { startRefactoringOf(code); } }
Single Responsibility Principle
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36. Or And?

37. Or if (code.isComplexOrUnreadable()) { doRefactoring(code); }
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38. Or if (code.isComplexOrUnreadable()) { doRefactoring(code); }
if (code.canBeImproved()) { doRefactoring(code); }
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39. And
if (isRefactoringPossibleAndJustifiedPredicate.apply(code, developer)) { doRefactoring(code); }
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40. And
if (isRefactoringPossibleAndJustifiedPredicate.apply(code, developer)) { doRefactoring(code); }
if (canStartRefactoringPredicate.apply(code, developer)) { doRefactoring(code); }
letstalkaboutjava.blogspot.com

41. Method’s name makes a difference

42. Method’s name makes a difference
refactoring.setState(IN_PROGRESS);
refactoring.setState(VERIFIED);
refactoring.setState(DONE);
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43. Method’s name makes a difference
refactoring.setState(IN_PROGRESS);
refactoring.setState(VERIFIED);
refactoring.setState(DONE);
refactoring.start(); refactoring.accepted(); refactoring.applied();
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44. Don’t show too much

45. Law of Demeter
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getMethodByName(refactoring.getScope()).getCondition(); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
letstalkaboutjava.blogspot.com

46. Law of Demeter
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getMethodByName(refactoring.getScope()).getCondition(); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getConditionOf(refactoring.getScope()); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
letstalkaboutjava.blogspot.com

47. Tell, don’t Ask
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getMethodByName(refactoring.getScope()).getCondition(); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getConditionOf(refactoring.getScope()); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
letstalkaboutjava.blogspot.com

48. Tell, don’t Ask
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getMethodByName(refactoring.getScope()).getCondition(); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getConditionOf(refactoring.getScope()); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
public void apply(ClassCode code, Refactoring refactoring) { code.apply(refactoring); }
letstalkaboutjava.blogspot.com

49. Asking many objects… Tell, don’t Ask
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getMethodByName(refactoring.getScope()).getCondition(); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
Asking many objects…
public void apply(ClassCode code, Refactoring refactoring) { Condition condition = code.getConditionOf(refactoring.getScope()); RefactoringApplier.applyRefactoringFor(condition, refactoring); }
public void apply(ClassCode code, Refactoring refactoring) { code.apply(refactoring); }
letstalkaboutjava.blogspot.com

50. Too much is… too much

51. Too much is… too much public class History { public void store(
Author author, RefactoringType type, Scope scope,
RefactoringJustification justification, Date today) { // some code }
letstalkaboutjava.blogspot.com

52. Too much is… too much public class History { public void store(
Author author, RefactoringType type, Scope scope,
RefactoringJustification justification, Date today) { // some code }
public class History { public void store(CodeDelta delta) { // some code }
letstalkaboutjava.blogspot.com

53. Input & Output

54. Input & Output
public void verify(Change change) { Refactoring refactoring = change.getRefactoring(); ClassCode affectedCode = change.getAffectedCode(); CodeUnit codeUnit = codeBaseRepository.findCodeUnitFor(affectedCode); codeUnit.applyRefactoringFor(affectedCode, refactoring); testsExecutor.runFor(codeUnit); }
letstalkaboutjava.blogspot.com

55. Input & Output
public void verify(Change change) { Refactoring refactoring = change.getRefactoring(); ClassCode affectedCode = change.getAffectedCode(); CodeUnit codeUnit = codeBaseRepository.findCodeUnitFor(affectedCode); codeUnit.applyRefactoringFor(affectedCode, refactoring); testsExecutor.runFor(codeUnit); }
public void verify(Change change) { ClassCode affectedCode = change.getAffectedCode(); CodeUnit codeUnit = codeBaseRepository.findCodeUnitFor(affectedCode); codeUnit.apply(change); testsExecutor.runFor(codeUnit); }
letstalkaboutjava.blogspot.com

56. (not so) easy choice

57. (not so) easy choice
public void triggerRefactoringProcessing(Refactoring refactoring){ switch (refactoring.state()) { case DEFINED: moveToInProgressState(refactoring); break; case IN_PROGRESS: createChangeFor(refactoring); break; case TO_VERIFY: verifyChangeFor(refactoring); break; case VERIFIED: applyChangeFrom(refactoring); break; } }
letstalkaboutjava.blogspot.com

58. (not so) easy choice
public void triggerRefactoringProcessing(Refactoring refactoring){ switch (refactoring.state()) { case DEFINED: moveToInProgressState(refactoring); break; case IN_PROGRESS: createChangeFor(refactoring); break; case TO_VERIFY: verifyChangeFor(refactoring); break; case VERIFIED: applyChangeFrom(refactoring); break; } }
private Map<RefactoringState, RefactoringTriggerStrategy> strategies; public RefactoringTrigger(Map<RefactoringState, RefactoringTriggerStrategy> strategies) { this.strategies = strategies; } public void triggerRefactoringProcessing(Refactoring refactoring){ strategies.get(refactoring.state()).triggerFor(refactoring); }
letstalkaboutjava.blogspot.com

59. State Pattern maybe? (not so) easy choice
public void triggerRefactoringProcessing(Refactoring refactoring){ switch (refactoring.state()) { case DEFINED: moveToInProgressState(refactoring); break; case IN_PROGRESS: createChangeFor(refactoring); break; case TO_VERIFY: verifyChangeFor(refactoring); break; case VERIFIED: applyChangeFrom(refactoring); break; } }
State Pattern maybe?
private Map<RefactoringState, RefactoringTriggerStrategy> strategies; public RefactoringTrigger(Map<RefactoringState, RefactoringTriggerStrategy> strategies) { this.strategies = strategies; } public void triggerRefactoringProcessing(Refactoring refactoring){ strategies.get(refactoring.state()).triggerFor(refactoring); }
letstalkaboutjava.blogspot.com

60. When you want to know too much…

61. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { if (change instanceof Refactoring) { processRefactoring(code, (Refactoring) change); } else if (change instanceof Improvement) { processImprovement(code, (Improvement) change); } else if (change instanceof Growth) { processGrowth(code, (Growth) change); } else { throw new UnsuportedChangeException(); } }

62. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { if (change instanceof Refactoring) { processRefactoring(code, (Refactoring) change); } else if (change instanceof Improvement) { processImprovement(code, (Improvement) change); } else if (change instanceof Growth) { processGrowth(code, (Growth) change); } else { throw new UnsuportedChangeException(); } }

63. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { if (change instanceof Refactoring) { processRefactoring(code, (Refactoring) change); } else if (change instanceof Improvement) { processImprovement(code, (Improvement) change); } else if (change instanceof Growth) { processGrowth(code, (Growth) change); } else { throw new UnsuportedChangeException(); } }

64. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { if (change instanceof Refactoring) { processRefactoring(code, (Refactoring) change); } else if (change instanceof Improvement) { processImprovement(code, (Improvement) change); } else if (change instanceof Growth) { processGrowth(code, (Growth) change); } else { throw new UnsuportedChangeException(); } }
public void triggerProcessingChangeOf(Code code, Change change) { change.accept(new ChangeProcessor(code)); }

65. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { change.accept(new ChangeProcessor(code)); }
public interface Change { void accept(Visitator visitator); }
public interface Visitator { void accept(Refactoring refactoring); void accept(Improvement improvement); void accept(Growth growth); }

66. When you want to know too much…
public void triggerProcessingChangeOf(Code code, Change change) { change.accept(new ChangeProcessor(code)); }
public interface Change { void accept(Visitator visitator); }
public interface Visitator { void accept(Refactoring refactoring); void accept(Improvement improvement); void accept(Growth growth); }
public class ChangeProcessor implements Visitator { @Override public void accept(Refactoring refactoring) { // some code } @Override public void accept(Improvement improvement) { // some code } @Override public void accept(Growth growth) { // some code }

67. Far too much…

68. Far too much…
public void process(Refactoring refactoring) { applyToCode(refactoring); createPullRequestWith(refactoring); doCodeReviewOf(refactoring); mergeToTheMaster(refactoring); }

69. Far too much…
public void process(Refactoring refactoring) { applyToCode(refactoring); createPullRequestWith(refactoring); doCodeReviewOf(refactoring); mergeToTheMaster(refactoring); }

70. Far too much…
public void process(Refactoring refactoring) { applyToCode(refactoring); createPullRequestWith(refactoring); doCodeReviewOf(refactoring); mergeToTheMaster(refactoring); }
public interface RefactoringProcessor { void process(Refactoring refactoring); }

71. Far too much…
public void process(Refactoring refactoring) { applyToCode(refactoring); createPullRequestWith(refactoring); doCodeReviewOf(refactoring); mergeToTheMaster(refactoring); }
public interface RefactoringProcessor { void process(Refactoring refactoring); }
public class CodeRefactoringProcessor implements RefactoringProcessor { @Override public void process(Refactoring refactoring) { applyToCode(refactoring); }

72. Far too much…
public void process(Refactoring refactoring) { applyToCode(refactoring); createPullRequestWith(refactoring); doCodeReviewOf(refactoring); mergeToTheMaster(refactoring); }
public interface RefactoringProcessor { void process(Refactoring refactoring); }
public class CodeRefactoringProcessor implements RefactoringProcessor { @Override public void process(Refactoring refactoring) { applyToCode(refactoring); }
public class PullRequestProcessor implements RefactoringProcessor { private final RefactoringProcessor processor; @Override public void process(Refactoring refactoring) { processor.process(refactoring); createPullRequestWith(refactoring); }

73. TL; DR

74. TL; DR Introduce private methods
Extract parts of the code organized around dependencies
Conditions
Switches
Single Responsibility Principle
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75. What was served?

76. What was served? What is Refactoring? Small changes No changes!!!
Readability
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77. What was served? What is Refactoring? Is it worth the effort?
It's not expensive
It's for any kind of project
letstalkaboutjava.blogspot.com

78. What was served? What is Refactoring? Is it worth the effort?
What you should know about Refactoring?
Refactoring vs. Redesign
Stay safe!
You have to know when to stop!
letstalkaboutjava.blogspot.com

79. What was served? What is Refactoring? Is it worth the effort?
What you should know about Refactoring?
How?
letstalkaboutjava.blogspot.com

80. Always leave the campground cleaner than you found it.
Boy Scouts Rule
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81. www.luxoft.com, @SebastianMalaca, letstalkaboutjava.blogspot.com

82. www.luxoft.com, @SebastianMalaca, letstalkaboutjava.blogspot.com

83. www.luxoft.com, @SebastianMalaca, letstalkaboutjava.blogspot.com