Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations. Each transformation (called a 'refactoring') does little, but a sequence of transformations can produce a significant restructuring. Since each refactoring is small, it's less likely to go wrong. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring.
This is a simple list of refactorings both from the original book and some later sources. Refactorings marked with 
with have some extra material to what's in the Refactoring book. Refactorings marked with 
are in addition to those in the refactoring book. Refactorings with Link Only are references to refactorings described elsewhere.
- Add Parameter
- Change Bidirectional Association to Unidirectional
- Change Reference to Value
- Change Unidirectional Association to Bidirectional
- Change Value to Reference
- Collapse Hierarchy
- Consolidate Conditional Expression
- Consolidate Duplicate Conditional Fragments
- Convert Dynamic to Static Construction by Gerard M. Davison
- Convert Static to Dynamic Construction by Gerard M. Davison
- Decompose Conditional
- Duplicate Observed Data
- Eliminate Inter-Entity Bean Communication (Link Only)
- Encapsulate Collection
- Encapsulate Downcast
- Encapsulate Field
- Extract Class
- Extract Interface
- Extract Method
- Extract Package by Gerard M. Davison
- Extract Subclass
- Extract Superclass
- Form Template Method
- Hide Delegate
- Hide Method
- Hide presentation tier-specific details from the business tier (Link Only)
- Inline Class
- Inline Method
- Inline Temp
- Introduce A Controller (Link Only)
- Introduce Assertion
- Introduce Business Delegate (Link Only)
- Introduce Explaining Variable
- Introduce Foreign Method
- Introduce Local Extension
- Introduce Null Object
- Introduce Parameter Object
- Introduce Synchronizer Token (Link Only)
- Localize Disparate Logic (Link Only)
- Merge Session Beans (Link Only)
- Move Business Logic to Session (Link Only)
- Move Class by Gerard M. Davison
- Move Field
- Move Method
- Parameterize Method
- Preserve Whole Object
- Pull Up Constructor Body
- Pull Up Field
- Pull Up Method
- Push Down Field
- Push Down Method
- Reduce Scope of Variable by Mats Henricson
- Refactor Architecture by Tiers (Link Only)
- Remove Assignments to Parameters
- Remove Control Flag
- Remove Double Negative by Ashley Frieze and Martin Fowler
- Remove Middle Man
- Remove Parameter
- Remove Setting Method
- Rename Method
- Replace Array with Object
- Replace Assignment with Initialization by Mats Henricson
- Replace Conditional with Polymorphism
- Replace Conditional with Visitor by Ivan Mitrovic
- Replace Constructor with Factory Method
- Replace Data Value with Object
- Replace Delegation with Inheritance
- Replace Error Code with Exception
- Replace Exception with Test
- Replace Inheritance with Delegation
- Replace Iteration with Recursion by Dave Whipp
- Replace Magic Number with Symbolic Constant
- Replace Method with Method Object
- Replace Nested Conditional with Guard Clauses
- Replace Parameter with Explicit Methods
- Replace Parameter with Method
- Replace Record with Data Class
- Replace Recursion with Iteration by Ivan Mitrovic
- Replace Static Variable with Parameter by Marian Vittek
- Replace Subclass with Fields
- Replace Temp with Query
- Replace Type Code with Class
- Replace Type Code with State/Strategy
- Replace Type Code with Subclasses
- Reverse Conditional by Bill Murphy and Martin Fowler
- Self Encapsulate Field
- Separate Data Access Code (Link Only)
- Separate Query from Modifier
- Split Loop by Martin Fowler
- Split Temporary Variable
- Substitute Algorithm
- Use a Connection Pool (Link Only)
- Wrap entities with session (Link Only)