Bad smells, Design Patterns, and Refactoring Michael Weiss 322005

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Bad smells, Design Patterns, and
RefactoringMichael Weiss3/2/2005
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Three related topics

• Common problems in programming
• Bad smell how not to do it
• Design Pattern how to do it
• Refactoring getting from (a) to (b)

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Duplicated Code

• Bad smell Fowler, p. 76.
• Design patterns (Jia, p.253 256)
• Method invocation
• Inheritance
• Delegation
• Refactoring
• Extract method (Fowler p.76, and Eclipse)
• Pull up method (Fowler p. 322, and Eclipse)
• Extract class (Fowler p. 149 Eclipse)

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Duplicated Code ? Method

• class A

method1 compute1 compute2 compute3
method2 compute1 compute2 compute3
problem local variables
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Duplicated Code ? Inheritance

• class A

method1 compute1 compute2 compute3
class B
method2 compute1 compute2 compute3
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Duplicated Code ? Delegation
class A
method1 helper.computeStuff()
class Helper
computeStuff compute1 compute2 compute3
helper
class B
method2 helper.computeStuff()
helper