Object-Oriented Programming is a paradigm that provides many concepts, such as inheritance, data binding, polymorphism, etc.
Simula is considered the first object-oriented programming language. The programming paradigm where everything is represented as an object is known as a truly 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.
The main aim of object-oriented programming is to implement real-world entities, for example, object, classes, abstraction, inheritance, polymorphism, etc.

Table of Contents

OOPs (Object-Oriented Programming System)

Object means a real-world entity such as a pen, chair, table, computer, watch, etc. Object-Oriented Programming is a methodology or paradigm to design a program using classes and objects. It simplifies software development and maintenance by providing some concepts:
• Object
• Class
• Inheritance
• Polymorphism
• Abstraction
• Encapsulation
Apart from these concepts, there are some other terms which are used in Object-Oriented design:
• Coupling
• Cohesion
• Association
• Aggregation
• Composition

java 109

Object

java 110

Any entity that has state and behavior is known as an object. For example, a chair, pen, table, keyboard, bike, etc. It can be physical or logical.
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: 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.

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.

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.

java 111

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.
Another example can be to speak something; for example, a cat speaks meow, dog barks woof, etc.
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.

java 112

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.

Coupling

Coupling refers to the knowledge or information or dependency of another class. It arises when classes are aware of each other. If a class has the details information of another class, there is strong coupling. In Java, we use private, protected, and public modifiers to display the visibility level of a class, method, and field. You can use interfaces for the weaker coupling because there is no concrete implementation.

Cohesion

Cohesion refers to the level of a component which performs a single well-defined task. A single well-defined task is done by a highly cohesive method. The weakly cohesive method will split the task into separate parts. The java.io package is a highly cohesive package because it has I/O related classes and interface. However, the java.util package is a weakly cohesive package because it has unrelated classes and interfaces.

Association

Association represents the relationship between the objects. Here, one object can be associated with one object or many objects. There can be four types of association between the objects:
• One to One
• One to Many
• Many to One, and
• Many to Many

Let’s understand the relationship with real-time examples. For example, One country can have one prime minister (one to one), and a prime minister can have many ministers (one to many). Also, many MP’s can have one prime minister (many to one), and many ministers can have many departments (many to many).

Association can be undirectional or bidirectional.

Aggregation

Aggregation is a way to achieve Association. Aggregation represents the relationship where one object contains other objects as a part of its state. It represents the weak relationship between objects. It is also termed as a has-a relationship in Java. Like, inheritance represents the is-a relationship. It is another way to reuse objects.

Composition

The composition is also a way to achieve Association. The composition represents the relationship where one object contains other objects as a part of its state. There is a strong relationship between the containing object and the dependent object. It is the state where containing objects do not have an independent existence. If you delete the parent object, all the child objects will be deleted automatically.

Advantage of OOPs over Procedure-oriented programming language

1) OOPs makes development and maintenance easier, whereas, in a procedure-oriented programming language, it is not easy to manage if code grows as project size increases.
2) OOPs provides data hiding, whereas, in a procedure-oriented programming language, global data can be accessed from anywhere.

java 113

Figure: Data Representation in Procedure-Oriented Programming

java 114

Figure: Data Representation in Object-Oriented Programming
3) OOPs provides the ability to simulate real-world event much more effectively. We can provide the solution of real word problem if we are using the Object-Oriented Programming language.

What is the difference between an object-oriented programming language and object-based programming language?

object-based programming language follows all the features of OOPs except Inheritance. JavaScript and VBScript are examples of object-based programming languages.
Do You Know?
• Can we overload the main method?
• A Java Constructor returns a value but, what?
• Can we create a program without main method?
• What are the six ways to use this keyword?
• Why is multiple inheritance not supported in Java?
• Why use aggregation?
• Can we override the static method?
• What is the covariant return type?
• What are the three usages of Java super keyword?
• Why use instance initializer block?
• What is the usage of a blank final variable?
• What is a marker or tagged interface?
• What is runtime polymorphism or dynamic method dispatch?
• What is the difference between static and dynamic binding?
• How downcasting is possible in Java?
• What is the purpose of a private constructor?
• What is object cloning?
What will we learn in OOPs Concepts?
• Advantage of OOPs
• Naming Convention
• Object and class
• Method overloading
• Constructor
• static keyword
• this keyword with six usage
• Inheritance
• Aggregation
• Method Overriding
• Covariant Return Type
• super keyword
• Instance Initializer block
• final keyword
• Abstract class
• Interface
• Runtime Polymorphism
• Static and Dynamic Binding
• Downcasting with instanceof operator
• Package
• Access Modifiers
• Encapsulation
• Object Cloning

So, this brings us to the end of blog. This Tecklearn ‘OOPs Concepts in Java’ blog helps you with commonly asked questions if you are looking out for a job in Java Programming. If you wish to learn Java and build a career Java Programming domain, then check out our interactive, Java and JEE Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

Java and JEE Training

Java and JEE Training

About the Course

Java and JEE Certification Training is designed by professionals as per the industrial requirements and demands. This training encompasses comprehensive knowledge on basic and advanced concepts of core Java & J2EE along with popular frameworks like Hibernate, Spring & SOA. In this course, you will gain expertise in concepts like Java Array, Java OOPs, Java Function, Java Loops, Java Collections, Java Thread, Java Servlet, and Web Services using industry use-cases and this will help you to become a certified Java expert.

Why Should you take Java and JEE Training?

• Java developers are in great demand in the job market. With average pay going between $90,000/- to $120,000/- depending on your experience and the employers.
• Used by more than 10 Million developers worldwide to develop applications for 15 Billion devices.
• Java is one of the most popular programming languages in the software world. Rated #1 in TIOBE Popular programming languages index (15th Consecutive Year)

What you will Learn in this Course?

Introduction to Java

• Java Fundamentals
• Introduction to Java Basics
• Features of Java
• Various components of Java language
• Benefits of Java over other programming languages
• Key Benefits of Java

Installation and IDE’s for Java Programming Language

• Installation of Java
• Setting up of Eclipse IDE
• Components of Java Program
• Editors and IDEs used for Java Programming
• Writing a Simple Java Program

Data Handling and Functions

• Data types, Operations, Compilation process, Class files, Loops, Conditions
• Using Loop Constructs
• Arrays- Single Dimensional and Multi-Dimensional
• Functions
• Functions with Arguments

OOPS in Java: Concept of Object Orientation

• Object Oriented Programming in Java
• Implement classes and objects in Java
• Create Class Constructors
• Overload Constructors
• Inheritance
• Inherit Classes and create sub-classes
• Implement abstract classes and methods
• Use static keyword
• Implement Interfaces and use it

Polymorphism, Packages and String Handling

• Concept of Static and Run time Polymorphism
• Function Overloading
• String Handling –String Class
• Java Packages

Exception Handling and Multi-Threading

• Exception handling
• Various Types of Exception Handling
• Introduction to multi-threading in Java
• Extending the thread class
• Synchronizing the thread

File Handling in Java

• Input Output Streams
• Java.io Package
• File Handling in Java

Java Collections

• Wrapper Classes and Inner Classes: Integer, Character, Boolean, Float etc
• Applet Programs: How to write UI programs with Applet, Java.lang, Java.io, Java.util
• Collections: ArrayList, Vector, HashSet, TreeSet, HashMap, HashTable

Java Database Connectivity (JDBC)

• Introduction to SQL: Connect, Insert, Update, Delete, Select
• Introduction to JDBC and Architecture of JDBC
• Insert/Update/Delete/Select Operations using JDBC
• Batch Processing Transaction
• Management: Commit and Rollback

Java Enterprise Edition – Servlets

• Introduction to J2EE
• Client Server architecture
• URL, Port Number, Request, Response
• Need for servlets
• Servlet fundamentals
• Setting up a web project in Eclipse
• Configuring and running the web app with servlets
• GET and POST request in web application with demo
• Servlet lifecycle
• Servlets Continued
• Session tracking and filter
• Forward and include Servlet request dispatchers

Java Server Pages (JSP)

• Fundamentals of Java Server Page
• Writing a code using JSP
• The architecture of JSP
• JSP Continued
• JSP elements: Scriptlets, expressions, declaration
• JSP standard actions
• JSP directives
• Introduction to JavaBeans
• ServletConfig and ServletContext
• Servlet Chaining
• Cookies Management
• Session Management

Hibernate

• Introduction to Hibernate
• Introduction to ORM
• ORM features
• Hibernate as an ORM framework
• Hibernate features
• Setting up a project with Hibernate framework
• Basic APIs needed to do CRUD operations with Hibernate
• Hibernate Architecture

POJO (Plain Old Java Object)

• POJO (Plain Old Java Object)
• Persistent Objects
• Lifecycle of Persistent Object

Spring

• Introduction to Spring
• Spring Fundamentals
• Advanced Spring

Got a question for us? Please mention it in the comments section and we will get back to you.

343