Refactoring: Improving the Design of Existing Code

Martin Fowler is the Chief Scientist of ThoughtWorks, an enterprise-application development and delivery company. He's been applying object-oriented techniques to enterprise software development for over a decade. He is notorious for his work on patterns, the UML, refactoring, and agile methods. Martin lives in Melrose, Massachusetts, with his wife, Cindy, and a very strange cat. His homepage is http://martinfowler.com.Kent Beck consistently challenges software engineering dogma, promoting ideas like patterns, test-driven development, and Extreme Programming. Currently affiliated with Three Rivers Institute and Agitar Software, he is the author of many Addison-Wesley titles.John Brant and Don Roberts are the authors of the Refactoring Browser for Smalltalk, which is found at http://st-www.cs.uiuc.edu/~brant/RefactoringBrowser/. They are also consultants who have studied both the practical and theoretical aspects of refactoring for six years. William Opdyke's doctoral research on refactoring object-oriented frameworks at the University of Illinois led to the first major publication on this topic. He is currently a Distinguished Member of Technical Staff at Lucent Technologies/Bell Laboratories. John Brant and Don Roberts are the authors of the Refactoring Browser for Smalltalk, which is found at http://st-www.cs.uiuc.edu/~brant/RefactoringBrowser/. They are also consultants who have studied both the practical and theoretical aspects of refactoring for six years.

1. Refactoring, a First Example. The Starting Point. The First Step in Refactoring. Decomposing and Redistributing the Statement Method. Replacing the Conditional Logic on Price Code with Polymorphism. Final Thoughts. 2. Principles in Refactoring. Defining Refactoring. Why Should You Refactor? When Should You Refactor? What Do I Tell My Manager? Problems with Refactoring. Refactoring and Design. Refactoring and Performance. Where Did Refactoring Come From? 3. Bad Smells in Code. Duplicated Code. Long Method. Large Class. Long Parameter List. Divergent Change. Shotgun Surgery. Feature Envy. Data Clumps. Primitive Obsession. Switch Statements. Parallel Inheritance Hierarchies. Lazy Class. Speculative Generality. Temporary Field. Message Chains. Middle Man. Inappropriate Intimacy. Alternative Classes with Different Interfaces. Incomplete Library Class. Data Class. Refused Bequest. Comments. 4. Building Tests. The Value of Self-testing Code. The JUnit Testing Framework. Adding More Tests. 5. Toward a Catalog of Refactorings. Format of the Refactorings. Finding References. How Mature Are These Refactorings? 6. Composing Methods. Extract Method. Inline Method. Inline Temp. Replace Temp with Query. Introduce Explaining Variable. Split Temporary Variable. Remove Assignments to Parameters. Replace Method with Method Object. Substitute Algorithm. 7. Moving Features Between Objects. Move Method. Move Field. Extract Class. Inline Class. Hide Delegate. Remove Middle Man. Introduce Foreign Method. Introduce Local Extension. 8. Organizing Data. Self Encapsulate Field. Replace Data Value with Object. Change Value to Reference. Change Reference to Value. Replace Array with Object. Duplicate Observed Data. Change Unidirectional Association to Bidirectional. Change Bidirectional Association to Unidirectional. Replace Magic Number with Symbolic Constant. Encapsulate Field. Encapsulate Collection. Replace Record with Data Class. Replace Type Code with Class. Replace Type Code with Subclasses. Replace Type Code with State/Strategy. Replace Subclass with Fields. 9. Simplifying Conditional Expressions. Decompose Conditional. Consolidate Conditional Expression. Consolidate Duplicate Conditional Fragments. Remove Control Flag. Replace Nested Conditional with Guard Clauses. Replace Conditional with Polymorphism. Introduce Null Object. Introduce Assertion. 10. Making Method Calls Simpler. Rename Method. Add Parameter. Remove Parameter. Separate Query from Modifier. Parameterize Method. Replace Parameter with Explicit Methods. Preserve Whole Object. Replace Parameter with Method. Introduce Parameter Object. Remove Setting Method. Hide Method. Replace Constructor with Factory Method. Encapsulate Downcast. Replace Error Code with Exception. Replace Exception with Test. 11. Dealing with Generalization. Pull Up Field. Pull Up Method. Pull Up Constructor Body. Push Down Method. Push Down Field. Extract Subclass. Extract Superclass. Extract Interface. Collapse Hierarchy. Form Template Method. Replace Inheritance with Delegation. Replace Delegation with Inheritance. 12. Big Refactorings. Tease Apart Inheritance. Convert Procedural Design to Objects. Separate Domain from Presentation. Extract Hierarchy. 13. Refactoring, Reuse, and Reality. A Reality Check. Why Are Developers Reluctant to Refactor Their Programs? A Reality Check (Revisited). Resources and References for Refactoring. Implications Regarding Software Reuse and Technology Transfer. A Final Note. References. 14. Refactoring Tools. Refactoring with a Tool. Technical Criteria for a Refactoring Tool. Practical Criteria for a Refactoring Tool. Wrap Up. 15. Putting It All Together. References. List of Soundbites. List of Refactorings. Index.