Object Oriented Analysis and Design Lecture 01 PDF

CS2101, SE2101, IT2101 Object Oriented Analysis and Design Lecture 01 Introduction to Object-Oriented Paradigm Bachelor of Science (Hons) in Computer Science | Software Engineering | Information Technology...

CS2101, SE2101, IT2101 Object Oriented Analysis and Design Lecture 01 Introduction to Object-Oriented Paradigm Bachelor of Science (Hons) in Computer Science | Software Engineering | Information Technology Department of Computing Faculty of Computing and Technology Saegis Campus Nugegoda Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 1  OOAD? Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 2  What is Object-Oriented Paradigm? Definition: A programming model where software design is organized around objects rather than functions and logic. Key Principle: Objects represent real-world entities and abstract details. Focus: Modular design with reusable components. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 3  Why Object-Oriented Programming (OOP)? Modularity: Code can be written and maintained in chunks. Reusability: Code can be reused across different projects. Scalability: Makes managing large codebases easier. Maintainability: Easier to fix or enhance parts of the system without affecting others. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 4  Why Object-Oriented Programming (OOP)? Modularity Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 5  Historical Evolution of Object Model (1) Simula (1960s): First Object-Oriented Language. Introduced Classes and Objects for simulation. Key feature: Inheritance for reusing code. Smalltalk (1970s): Developed by Alan Kay. Added Messaging and formalized Encapsulation. First to introduce Polymorphism. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 6  Historical Evolution of Object Model (2) C++ (1980s): Added object-oriented features to C. Inheritance, Polymorphism, and Abstraction became widely used. Java (1990s): Widespread popularity with cross-platform support. Garbage collection and strong OOP features. — Garbage collection in Java is the automated process of deleting code that's no longer needed or used. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 7  Fundamental Concepts of OOP (1) Abstraction: Hides complex implementation details, exposes only what’s necessary. Example: A car interface with "drive" method, hiding the internal engine workings. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 8  Abstraction – Example: Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 9  Fundamental Concepts of OOP (2) Encapsulation (Information Hiding): Combines data (attributes) and methods (behavior) into a single unit (class). Controls access to data through getter and setter methods. Example: Bank account with balance (private), accessed only via deposit and withdraw methods. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 10  Encapsulation - Example Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 11  Fundamental Concepts of OOP (3) Inheritance: Enables new classes to inherit properties and methods from existing ones. Parent-Child relationship: Child class extends or overrides behavior. Example: A class Vehicle inherited by Car and Truck. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 12  Inheritance – Example: Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 13  Fundamental Concepts of OOP (4) Polymorphism: Poly (many) + morphism (forms) Allows objects to be treated as instances of their parent class while retaining their own unique methods. Two types: Compile-time (method overloading) Run-time (method overriding) Example: A Shape class with subclasses Circle and Square, each having its own implementation of draw() method. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 14  Polymorphism – Example: Speak(); Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 15  What is an Object? Definition: A real-world entity modeled in code. Object = State + Behavior. State: Represented by attributes (data fields). Behavior: Represented by methods (functions). Example: Object: A Car State: Color, Model, Speed How to draw the structure Behavior: Drive, Stop of this object? Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 16 Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 17  What is a Class? Class Definition: A blueprint for creating objects. Components: Attributes: Variables that hold data. Methods: Functions that define behaviors. Example: Class Car with attributes color, model, and methods drive(), stop(). How to draw the structure of this object? Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 18  Draw the structure of this What is a Class? class???? Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 19  Object Relationships: Association Association: A general relationship between objects of different classes. Example: A student attends multiple courses; each course has multiple students. Represented as: Student Course Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 20  Object Relationships: Aggregation Aggregation: A "has-a" relationship where one object contains other objects. Weak relationship: Contained objects can exist independently. Example: A Library has Books, but the Books can exist without the Library. Represented as: Library Books Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 21  Object Relationships: Composition Composition: A stronger form of aggregation. Strong relationship: Contained objects cannot exist without the container. Example: A House and Rooms – if the house is destroyed, the rooms no longer exist. Represented as: House Rooms Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 22  Object Relationships: Inheritance Inheritance: A relationship where one class (child) inherits properties and methods from another class (parent). Is-a relationship: A specific type of general class. Example: Dog is a Mammal, so it inherits characteristics from the Mammal class. Represented as: Mammal Dog Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 23  Key points OOP is a paradigm based on objects. Key concepts: Abstraction, Encapsulation, Inheritance, Polymorphism. Objects and Classes form the foundation of OOP. Relationships between objects enhance the structure of a system. Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 24  In class activity: Identify Real-World Objects Instructions: Get into small groups (5 members for each group). Pick a real-world object (e.g., car, bank account, library, smartphone). Identify: Attributes Behaviors Class Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 25 Ms. Chathurangi Dhanushika Weerasinghe, MSc UCSC(Col), BSc (Ruh) Saegis Campus 26