DEV Community: Abinaya V

OOP concepts in Java:

Abinaya V — Sat, 27 Jun 2026 11:43:44 +0000

1. Object
An object is an instance of a class. It represents a real-world thing and contains data (variables) and behavior (methods).

2. Class
A class is a blueprint/template used to create objects.

3. Encapsulation
Encapsulation means wrapping data and methods into one unit (class) and protecting data using access modifiers.

4. Abstraction

 Abstraction means hiding implementation details and showing only important information.

5. Polymorphism
Polymorphism means one thing having many forms.

6.Inheritance
Inheritance is an OOP concept where one class acquires (inherits) properties and methods of another class.

Short Interview Definition:

Class: Blueprint for creating objects
Object: Instance of a class
Encapsulation: Binding data and methods together
Abstraction: Hiding internal details
Polymorphism: One name, multiple behaviors

About Backend

Abinaya V — Fri, 26 Jun 2026 11:17:57 +0000

What is Backend?

Backend is the server-side part of an application that handles the logic, database, security, and communication between the user interface (frontend) and the server.

Simple flow:
User → Front End → Back End → Database → Back End → Front End → User

Back End Programming Languages:

Java
python
JavaScript (Node.js)
PHP
C Sharp
Ruby
Go

Back End Languages Comparison

Language	Difficulty	Speed	Popular Framework	Best Used For
Java	Medium	Fast	Spring Boot	Enterprise apps, banking, large systems
Python	Easy	Medium	Django, Flask	Web apps, AI, data science
JavaScript (Node.js)	Easy	Fast	Express.js	Real-time apps, APIs, web apps
PHP	Easy	Medium	Laravel	Websites, CMS, web development
C#	Medium	Fast	ASP.NET Core	Microsoft apps, enterprise software, games
Ruby	Easy	Medium	Ruby on Rails	Startups, quick web development
Go (Golang)	Medium	Very Fast	Gin, Echo	Cloud services, high-performance APIs

Backend task
A backend can:

Process user logins
Store and retrieve data from databases
Handle payments
Send emails and notifications
Provide APIs for mobile and web apps

How to find simple error in java

Abinaya V — Wed, 24 Jun 2026 17:09:40 +0000

Introduction to Java

Abinaya V — Mon, 22 Jun 2026 18:40:41 +0000

Java is a high-level, object-oriented, platform-independent programming language developed by Sun Microsystems in 1995 (now owned by Oracle Corporation).

The founder (creator) of Java is James Gosling.

Originally, Java was called Oak, and it was designed for electronic devices. Later it was renamed Java and became popular for web, mobile, and enterprise applications.

Compiler
A compiler is a software program that converts the source code written by a programmer into machine language (binary code) so that the computer can understand and execute it.

Simple meaning:
Compiler = A translator that changes human-written code → computer-understandable code

There are two types of Translation

Compiler Translation:

 Compiler Translation means converting a program written in a high-level programming language into a language that a computer can understand.

Interpreter Translation :

 An Interpreter is a program that reads and executes code line by line without converting the whole program at once.

In java we use Interpreter Translation line bye line execution.

Basic problem python

Abinaya V — Sat, 13 Jun 2026 16:52:53 +0000

Browser Router

Abinaya V — Thu, 28 May 2026 09:16:19 +0000

Browser Router means

Browser Router is a component in React Router used for navigation in React applications.
It allows your app to change pages without reloading the browser.

How Browser Router Works

*Syntax *

<BrowserRouter>
<Routes>
<Route path="/" element={<Home />} />
<Route path="/about" element={<About />} />
</Routes>
</BrowserRouter>

Navigating via links using,

 <Link to="/about">Go to About</Link>

Example :

looping in python

Abinaya V — Wed, 27 May 2026 09:10:16 +0000

Loops are used to repeat a block of code multiple times.

Python has mainly 2 types of loops:

for loop
while loop

1.for Loop

   Used when the number of iterations is known.

Example
input:

  for i in range(5):
     print(i)

output:

2.while loop

Used when the condition should run until it becomes false.

example
input:

  i = 1
  while i <= 5:
   print(i)
     i += 1

output:

About Hookes in React

Abinaya V — Mon, 18 May 2026 20:32:14 +0000

React Hooks

React Hooks are special functions in React that let you use state and other React features inside functional components. Before Hooks, state was mainly used in class components. Hooks made functional components more powerful and easier to write.

Why Hooks are Used

Hooks help you:

Store data in components
Handle user actions
Manage lifecycle methods
Reuse logic
Work with APIs
Improve code readability

Common React Hooks
Used to store and update data.

Virtual DOM and Real DOM in React

 **Real DOM**
  The Real DOM is the actual webpage structure shown in the browser.

When HTML loads in the browser, the browser creates a tree structure called the DOM (Document Object Model).

**Example HTML**
   <h1>Hello</h1>

output
Document
└── h1
└── "Hello"

Problem with Real DOM
Updating the Real DOM is:

slow
expensive
Affects performance

Virtual DOM

The Virtual DOM is a lightweight copy of the Real DOM used by React.
React first updates the Virtual DOM, compares changes, then updates only the changed parts in the Real DOM.

Diffing Algorithm in React
The Diffing Algorithm is the process React uses to compare:

old virtual DOM
new Virtual DOM

and find what changed.

Basic function in React

Abinaya V — Thu, 14 May 2026 16:50:30 +0000

App jsx
App.jsx is the main component file in a React application created using Vite or Create React App.

Why .jsx?
.jsx means JavaScript XML

It allows writing HTML inside JavaScript:

example

 const element = <h1>Hello</h1>;

JSX Rules in React

1. Return Only One Parent Element

2. Close All Tags

3. Use className Instead of class

4. Use Curly Braces {} for JavaScript

5. Inline CSS Uses Object

6. Attribute Names Use camelCase

7. JavaScript Expressions Allowed

8. Components Start with Capital Letter

9. Comments in JSX

10. Use htmlFor Instead of for.

Components in React
Components are reusable pieces of UI in React.
They help divide the application into small independent parts.

Examples

Header
Navbar
Footer
Login Form
Card

React in javascript

Abinaya V — Thu, 14 May 2026 08:38:21 +0000

React
React is a JavaScript library used to build user interfaces, especially web applications.

It was created by Meta (formerly Facebook).

Simple meaning
JavaScript → programming language
React → library built using JavaScript

** NPM Means:**
npm stands for Node Package Manager.

It is used to:

Install JavaScript packages/libraries
Manage project dependencies
Run scripts in projects

npm comes automatically when you install Node.js.

MPA

In web development, MPA means Multi-Page Application.

A Multi-Page Application loads a new HTML page from the server whenever the user moves to another page.

SPA

SPA means Single Page Application.

A Single Page Application loads only one HTML page initially, then updates content dynamically without reloading the entire page.

Difference between libraries and frameworks?

Promise in javascript

Abinaya V — Thu, 07 May 2026 11:26:45 +0000

A Promise in JavaScript is an object that represents the result of an asynchronous operation.

It helps handle tasks like:

API calls
File loading
Database requests
Timers (setTimeout)

Instead of waiting for the task to finish, JavaScript continues running other code.

Promise States

A Promise has 3 states:

Pending → Initial state
Resolved / Fulfilled → Operation successful
Rejected → Operation failed

Promise Methods

Method and Purpose

.then() -> Runs when promise is successful

.catch() -> Runs when promise fails

.finally() -> Runs always

output

Callback Hell.

output

Closure in JavaScript

Abinaya V — Wed, 06 May 2026 13:04:11 +0000

A closure is a function that remembers and accesses variables from its outer scope even after the outer function has finished executing.

Retains access to outer function variables.
Preserves the lexical scope.
Allows data encapsulation and privacy.
Commonly used in callbacks and asynchronous code.

For example