Note for DESIGN PATTERN - dp By JNTU Heroes

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LECTURE NOTES ON DESIGN PATTERNS IV B. Tech I semester (JNTUH-R13) INFORMATION TECHNOLOGY 1

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CONTENTS UNIT-I Introduction: 1. 2. 3. 4. 5. 6. 7. 8. What is a design pattern? Design patterns in Smalltalk MVC Describing Design Patterns The Catalog of Design Patterns Organizing the Catalog How Design Patterns Solve Design Problems How to Select a Design Pattern How to use a Design Pattern. UNIT-II A Case Study: 1. Designing a Document Editor Design Problems, 2. Document Structure 3. Formatting 4. Embellishing the User Interface 5. Supporting Multiple Look-and Feel Standards 6. Supporting Multiple Window Systems, 7. User Operations Spelling Checking and Hyphenation, 8. Summary. 9. Creational Patterns: Abstract Factory 10. Builder 11. Factory Method 12. Prototype 13. Singleton 14. Discussion of Creational Patterns UNIT-III Structural Pattern Part-I : 1. Adapter 2. Bridge 3. Composite Structural Pattern Part-II : 1. 2. 3. 4. Decorator Façade Flyweight Proxy 2

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UNIT-IV Behavioural Patterns Part-I : 1. Chain of Responsibility 2. Command 3. Interpreter 4. Iterator Behavioural Patterns Part-II : 1. Mediator 2. Memento 3. Observer UNIT-V Behavioural Patterns Part-II (cont’d): 1. 2. 3. 4. 5. State Strategy Template Method Visitor Discussion of Behavioral Patterns 6. What to Expect from Design Patterns 7. A Brief History 8. The Pattern Community An Invitation 9. A Parting Thought UNIT -I 3

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Introduction What is a Design Pattern? • Each pattern Describes a problem which occurs over and over again in our environment ,and then describes the core of the problem • Novelists, playwrights and other writers rarely invent new stories. • Often ideas are reused, such as the “Tragic Hero” from Hamlet or Macbeth. • Designers reuse solutions also, preferably the “good” ones – Experience is what makes one an ‘expert’ • Problems are addressed without rediscovering solutions from scratch. “My wheel is rounder. Design Patterns are the best solutions for the re-occurring problems in the application programming environment. • Nearly a universal standard. • Responsible for design pattern analysis in other areas, including GUIs. • Mainly used in Object Oriented programming. Design Pattern Elements 1. Pattern Name Handle used to describe the design problem. Increases vocabulary. Eases design discussions. Evaluation without implementation details. 2. Problem Describes when to apply a pattern. May include conditions for the pattern to be applicable. Symptoms of an inflexible design or limitation. 3. Solution Describes elements for the design. Includes relationships, responsibilities, and collaborations. Does not describe concrete designs or implementations. A pattern is more of a template. 4. Consequences 4