Object Oriented Programming Explained

Object Oriented Programming Paradigm

• OOP is a programming paradigm where program components are represented as objects
• An object is a real-world entity possessing a state and exhibiting behavior
• Objects can be physical (tangible) or logical (intangible)
• Objects bundle data (state) and procedures (behavior) cohesively
• OO uses local data stored in objects, unlike procedural programming which uses global shared data
• OO programming allows applications to comprise objects requesting respective services
• OO programming languages include Eiffel, Smalltalk, C++, and Java

Characteristics of Object-Oriented Programming

• Object-oriented programming has five characteristics
• Everything is an object; it stores data and performs operations on itself
• A program consists of objects communicating by sending messages
• An object contains its own memory of other objects
• Every object has a type, each object is an instance of a class
• An object of a particular type can receive the same messages

Class and Object Concepts

• A class defines objects of the same type
• A class is a template or blueprint that defines an object's data fields (state) and operations (behavior)
• An object is an instance of a class, that can have many instances
• Creating an instance is instantiation
• "Object" and "instance" are often interchangeable
• Designing an object-oriented program involves creating classes and defining them, using OO-based programming languages like Java
• Class design entails specifying attributes (data variables) and behaviors (operations)
• A class introduces a new data type in OOP
• A class is a logical concept, while an object is a physical component
• In defining a "circle" class, the "radius" variable represents the state of circle objects and characterizes the circle, with current values representing different objects
• You may define operations named "getArea()" and "getPerimeter()" that can be used on defined circle objects
• In the rectangle class, "width" and "height" represent the state of any rectangle
• Current values of the width and height represent different objects of the class rectangle
• The behavior of rectangle objects is defined by "getArea()" and "getPerimeter()"

Abstraction and Encapsulation

• Abstraction displays relevant object attributes while hiding unnecessary details
• Driving a car is an example because the driver is only concerned with the actions of accelerating, breaking and starting/stopping
• Abstraction reduces programming effort and complexity
• Abstraction allows the end-user to use the features without needing to know underlying implementation details
• Encapsulation combines data and associated functions into a single class
• Encapsulation hides object state from the outside world, making a set of public methods available to access the state
• Encapsulation, achieved when objects keep state private, is an information-hiding mechanism
• Encapsulation exists to hide internal object workings from outside access, so changing later will not impact outside clients

Benefits of Object-Oriented Programming

• Simplicity is achieved because software objects model real-world objects simplifying complexity and improving the structure
• Modularity is achieved because each object forms a separate entity decoupled from the rest of the system
• Modifiability exists because it is easy to make minor changes in the data representation or the procedures, changes inside a class are isolated using the information hiding principle
• Extensibility is achieved by adding new objects and modifying existing ones
• Maintainability objects can be maintained separately, making locating and fixing problems easier
• Re-usability of objects allows usage in different programs