1. Refactoring 101 William C. Wake William.Wake@acm.org 2-2-2000

2. Refactoring

3. Agenda l “Code smells” l Solid set of unit tests l Refactorings l Demo l Questions/Discussion

4. Code Smells “If it stinks, change it.” l Duplicate code l Switch statements l Long method l Large class l Data class (“data bag”) l Long parameter list l Primitive obsession l Temporary field l etc.

5. Unit Tests l Automatic l Self-checking l Run often (almost constantly) l “If you want to refactor, the essential precondition is having solid tests.” -- M. Fowler

6. JUnit l Unit testing tool l Supports creating and running test suites l Available for Java & several other languages l http://xprogramming.com

7. Refactorings l Fowler’s book has a catalog l There are many more l Often reversible l Pay attention to the mechanics l Let the compiler tell you l Small steps with constant tests

8. Extract Method

9. Encapsulate Field

10. Introduce Null Object

11. Parameterize Method WebService handleGet(…) handlePut(…) handle(serviceType,…)

12. Replace Constructor with Factory Method

13. Replace String with Stringbuffer

14. Demo l Hand out real code seeded with refactoring opportunities l Audience takes 5 minutes to identify smells l Audience helps refactor in IDE l Observe the motion back and forth between test and code

15. Discussion Questions?

16. More Information l Refactoring, by Martin Fowler l Extreme Programming Explained, by Kent Beck l Anything by Jon Bentley - Programming Pearls, More Programming Pearls, Writing Efficient Programs