JAVA: OOPS Concept
Java
· Java is a popular programming language, created in 1995.
· It is owned by Oracle, and more than 3 billion devices run Java.
· Java is a programming language and a platform. Java is a high level, robust, object-oriented and secure programming language
Object Oriented Programming (OOPs)
· Object-Oriented Programming or OOPs refers to languages that uses objects in programming.
· Object-oriented programming aims to implement real-world entities like inheritance, hiding, polymorphism etc. in programming.
· The main aim of OOP is to bind together the data and the functions that operate on them so that no other part of the code can access this data except that function.
· Simula is considered the first object-oriented programming language.
· Smalltalk is considered the first truly object-oriented programming language.
The popular object-oriented languages are
· Java
· C#
· PHP
· Python
· C++ etc.
Concepts in OOPs
· Object
· Class
· Inheritance
· Polymorphism
· Abstraction
· Encapsulation
1. Object
· Any entity that has state and behavior is known as an object.
· An Object can be defined as an instance of a class.
· An object contains an address and takes up some space in memory.
· Objects can communicate without knowing the details of each other’s data or code.
· The only necessary thing is the type of message accepted and the type of response returned by the objects.
Example:
i. A dog is an object because it has states like color, name, breed, etc. as well as behaviors like wagging the tail, barking, eating, etc.
ii. A chair, pen, table, keyboard, bike, etc. It can be physical or logical.
2. Class
· Collection of objects is called class.
· It is a logical entity.
· A class can also be defined as a blueprint from which you can create an individual object.
· Class doesn’t consume any space.
3. Inheritance
· When one object acquires all the properties and behaviors of a parent object, it is known as inheritance.
· It provides code reusability.
· It is used to achieve runtime polymorphism.
4. Polymorphism
If one task is performed in different ways, it is known as polymorphism.
For example: to convince the customer differently, to draw something, for example, shape, triangle, rectangle, etc.
In Java, we use method overloading and method overriding to achieve polymorphism.
5. Abstraction
Hiding internal details and showing functionality is known as abstraction.
For example, phone call, we don’t know the internal processing.
In Java, we use abstract class and interface to achieve abstraction.
6. Encapsulation
Binding (or wrapping) code and data together into a single unit are known as encapsulation.
For example, a capsule, it is wrapped with different medicines.
A java class is the example of encapsulation. Java bean is the fully encapsulated class because all the data members are private here.
