Refactoring 101

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Refactoring 101

• William C. Wake
• William.Wake_at_acm.org
• 2-2-2000

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Refactoring
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Agenda

• Code smells
• Solid set of unit tests
• Refactorings
• Demo
• Questions/Discussion

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Code SmellsIf it stinks, change it.

• Duplicate code
• Switch statements
• Long method
• Large class
• Data class (data bag)

• Long parameter list
• Primitive obsession
• Temporary field
• etc.

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Unit Tests

• Automatic
• Self-checking
• Run often (almost constantly)
• If you want to refactor, the essential
  precondition is having solid tests. -- M. Fowler

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JUnit

• Unit testing tool
• Supports creating and running test suites
• Available for Java several other languages
• http//xprogramming.com

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Refactorings

• Fowlers book has a catalog
• There are many more
• Often reversible
• Pay attention to the mechanics
• Let the compiler tell you
• Small steps with constant tests

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Extract Method
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Encapsulate Field
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Introduce Null Object
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Parameterize Method
WebService
WebService
handleGet()
handle(serviceType,)
handlePut()
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Replace Constructor with Factory Method
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Replace String with Stringbuffer
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Demo

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

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Discussion
Questions?
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More Information

• Refactoring, by Martin Fowler
• Extreme Programming Explained, by Kent Beck
• Anything by Jon Bentley - Programming Pearls,
  More Programming Pearls, Writing Efficient
  Programs