Object Oriented Programming Concepts

Object Oriented concepts used in Software Engineering

Object: - An object is something which is capable of being seen, touched or sensed. Each object has certain distinctions or attributes which enable you to recognize and classify it. Each object has certain actions or methods associated with it.

Class: - A class encapsulates data and procedural abstractions required to describe the content and behavior of some real world entity. A class is a generalized description that describes a collection of similar objects.

Encapsulation: - An object is said to be encapsulate (hide) data and program. This means that the user cannot see the inside of the object but can use the object by calling the program part of the object. This hiding of details of one object from another object, which uses it, is known as encapsulation.

Inheritance: - Inheritance is defined as the property of objects by which instances of a class can have access to data and programs contained in a previously defined class, without those definitions being restated. Classes are linked together in a hierarchy. They form a tree, whose root is the class of “objects”. Each class (except for the root class) will have a super class (a class above it in the hierarchy) and possibly subclasses. A class can inherit (i.e. acquire) methods from its super class and in turn can pass methods on to its subclasses. A subclass must have all the properties of the parent class and other properties as well.

Polymorphism: - Polymorphism includes the ability to use the same message to objects of different classes and have them behave differently. Thus we could define the message “+” for both the addition of numbers and the concatenation (joining) of characters. Polymorphism provides the ability to use the same word to invoke different methods, according to similarity of meaning.

Object/class associations: - Objects/classes interact with each other. Multiplicity defines how many instances of one object/class can be associated with one instance of another object/class.

Messages: - The interaction or communication between the different objects and classes is done by passing messages. The object, which requires communicating with another object, will send a request message to the latter. A message can be sent between two objects only if they have an association between them.