The document discusses refactoring code to improve its design without changing its external behavior. It defines refactoring as improving the code's internal structure to make it easier to understand and modify. The goals of refactoring are to remove duplication, simplify complex logic, clarify unclear code, and make the code easier to maintain without adding new functionality. It recommends refactoring when adding features, fixing bugs, or during code reviews. It also lists common "bad smells" in code and examples of refactoring techniques like extracting methods, moving methods, encapsulating fields, using interfaces, removing unused parameters, and replacing nested conditionals with guard clauses.

1. Clean Code Refactoring 1

2. Refactoring Any fool can write code that a computer can understand. Good programmers write code that humans can understand. 2

3. Refactoring What is Refactoring? Martin Fowler : "a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior“. William C. Wake : "Refactoring is the art of safely improving the design of existing code“. 3

4. Refactoring The process of refactoring involves the removal of duplication, the simplification of complex logic, and the clarification of unclear code. The goal of refactoring is NOT to add new functionality The goal is refactoring is to make code easier to maintain in the future 4

6. Refactor When You Need to Fix a Bug

7. Refactor As You Do a Code Review5

8. Refactoring The Refactoring Cycle Choose the worst smell Select a refactoring that will address the smell Apply the refactoring 6

10. Long Method

11. Large Class

12. Long Parameter List

13. Divergent Change

14. Shotgun Surgery

15. Feature Envy

16. Data Clumps

17. Primitive Obsession

18. Switch Statements

19. Parallel Inheritance Hierarchies

20. Lazy Class

21. Speculative Generality

22. Temporary Field

23. Message Chains

24. Middle Man7

26. Alternative Classes with Different Interfaces

27. Incomplete Library Class

28. Data Class

29. Refused Bequest

30. Comments8

31. void printOwing() { printBanner(); //print details System.out.println ("name: " + _name); System.out.println ("amount " + getOutstanding()); } Refactoring Extract Method void printOwing() { printBanner(); //print details System.out.println ("name: " + _name); System.out.println ("amount " + getOutstanding()); } Reusability High Cohesion Readability void printOwing() { printBanner(); printDetails(getOutstanding()); } Void printDetails (double outstanding) { System.out.println ("name: " + _name); System.out.println ("amount " + outstanding); } Polymorphism 9

32. Refactoring Move Method 10

33. Refactoring Move Method low Coupling High Cohesion 11

34. Refactoring Encapsulate Field you should never make your data public. When you make data public, other objects can change and access data values without the owning object's knowing about it. 12

35. Refactoring Extract Interface 13

36. Refactoring Remove Parameter A parameter is no longer used by the method body. Remove it. 14

37. Refactoring Replace Nested Conditional with Guard Clauses A method has conditional behavior that does not make clear the normal path of execution. Use guard clauses for all the special cases. Readability 15

38. Refactoring Visit our Page on Facebook! 16