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Design Patterns in Java and .NET

Tim MurphyTechnical Specialist

Mike VogtVice President of Architecture

Objective• Show the usefulness of Design Patterns

when developing applications and how they apply no matter what the platform.

Agenda• History of patterns• What are patterns• Why are patterns important• Explore 6 common patterns• Anti-Patterns

History Of Patterns• Gang Of Four• POSA – Patterns of

Software Architecture• Patterns of Enterprise

Application Architecture

What Are Patterns

• Pattern Name• Problem• Solution• Consequences

Why Are Patterns Important• Common vocabulary• Repositories of common solutions

Factory Method Pattern• Method for object creation• Lets subclasses decide which classes

to create

Decorator Pattern

• Attach additional responsibilities to an object dynamically

• Allows behavior to be added via “wrappers”

• Avoids extensive inheritance hierarchies

cost()

Whip

cost()

Mocha

cost()DarkRoast

Adapter Pattern• Allows a system to use methods that

do not match their interface

Visitor Pattern• A way of separating an algorithm from

an object structure it operates on.• One can add new operations to

existing object structures without modifying those structures<<interface>>

CarElement

+ accept(CarElementVisitor v)

Wheel Engine Body Car

Strategy Pattern• Interchangeable algorithms

Composite Pattern• Allows you to compose objects into

tree structures to represent whole-part hierarchies.

• Lets clients treat individual objects and compositions of objects uniformly.

Node

Leaf Leaf Leaf

<<interface>>Component

+ operation+ add(Component c)+ remove(Component c)+ getChild(int i)

Leaf

+ operation()

Composite

add, remove, getChild, operation

Client

Anit-Patterns• One pattern to rule them all• Loosey Goosey

ResourcesDesign Patterns: Elements of Reusable Object-Oriented Software – Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides

Head First Design Patterns – Eric Freeman and Elisabeth Freeman

Design Patterns In C# - Steven John Metsker

Thank You!Blogs –

geekswithblogs.net/tmurphy

Email -tmurphy@psclistens.commvogt@psclistens.com

Twitter –@twmurph@mvogt99

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