DEV Community: Raja B

Constructor

Raja B — Mon, 05 Oct 2026 09:19:02 +0000

A constructor in Java is a special member that is called when an object is created. It initializes the new object’s state. It is used to set default or user-defined values for the object's attributes

A constructor does not have a return type, not even void.
A constructor is called automatically when an object is created using new.
Constructors can have parameters and can be overloaded.

Reference

https://www.geeksforgeeks.org/java/constructors-in-java/

Java Basic Concepts

Raja B — Sat, 26 Sep 2026 10:37:53 +0000

Object-Oriented Programming (OOP) is a programming style that organizes code around objects—things that contain both data and actions. The four core OOP concepts are encapsulation, abstraction, inheritance, and polymorphism.

Basic building blocks

Before the four pillars, understand these two terms:

Term	Meaning	Real-life example
Class	A blueprint/template for creating objects	A Car design
Object	A real item created from a class	A specific red Tesla car

In Java:

class Car 
{
    String brand;
    int speed;

    void drive() 
    {
        System.out.println(brand + " is driving");
    }
}

Car car1 = new Car();
car1.brand = "Tesla";
car1.speed = 100;

car1.drive();

Here:

Car is the class
car1 is an object
brand and speed are data/properties
drive() is an action/method

An object is a software bundle of related state (data) and behavior (methods)

The four OOP concepts

Concept	Simple meaning	Main purpose
Encapsulation	Protect data inside an object	Control and validate data changes
Abstraction	Show only what is needed	Hide unnecessary complexity
Inheritance	Child class reuses parent class features	Reduce repeated code
Polymorphism	Same method call, different behavior	Write flexible code

Reference:

Language for java

Raja B — Tue, 22 Sep 2026 09:22:35 +0000

Programming Language History

1. Based on computer level

Type	Meaning	Examples	Simple idea
Machine language	Instructions written as binary 0s and 1s, directly understood by the CPU	10110000...	Very fast but extremely hard for humans
Assembly language	Uses short codes instead of raw binary; converted to machine code by an assembler	MOV, ADD	Closer to hardware
High-level language	Easier for humans to read and write; translated into machine instructions	JavaScript, Python, Java, C, C++	Used for most modern applications

2. Based on programming style

This classification is called a programming paradigm—the style or method used to solve a problem.

Types of Programming language

Programming languages are ways to give instructions to a computer...
Like human languages (Tamil, English), each programming language has its own rules and syntax...
But remember: one language can belong to more than one type—for example, JavaScript supports procedural, object-oriented, and functional styles...

1.Procedural programming

In procedural programming, you write a sequence of instructions, usually organized into functions/procedures

function calculateTotal(price, quantity) 
{
  return price * quantity;
}

let total = calculateTotal(100, 3);
console.log(total); // 300

The computer follows steps: get values → call function → calculate → show result

Common examples: C, Pascal, JavaScript, Python
Useful for: simple programs, algorithms, step-by-step tasks
Think of it as: a cooking recipe with ordered steps

2. Object-oriented programming (OOP)

OOP organizes code using objects. An object combines data (properties) and actions (methods)

const student = {
  name: "Arun",
  marks: 85,

  showResult() {
    console.log(`${this.name} scored ${this.marks}`);
  }
};

student.showResult();

Here, student is an object. It has data (name, marks) and behavior (showResult).

Common examples: Java, C++, C#, JavaScript, Python
Main concepts: objects, classes, encapsulation, inheritance, polymorphism
Useful for: large applications such as e-commerce sites, games, banking apps, and React-style UI modeling

3. Functional programming

Functional programming focuses on functions that take input and return output. It tries to avoid changing existing data unexpectedly

const prices = [100, 200, 300];

const discountedPrices = prices.map(function (price) {
  return price * 0.9;
});

console.log(discountedPrices); // [90, 180, 270]

Common examples: Haskell, Lisp, Scala, JavaScript
JavaScript supports functional methods such as map(), filter(), and reduce()
Useful for: data transformation and writing predictable code

4. Scripting languages

Scripting languages are commonly used to automate tasks, add interactivity, or control other software

document.querySelector("button").addEventListener("click", function () {
  alert("Button clicked!");
});

This JavaScript code makes a web page interactive when a user clicks a button

Common examples: JavaScript, Python, PHP, Ruby, Bash
Useful for: web pages, automation, browser interactions, server-side scripting
JavaScript is the main scripting language of the browser

5. Logic programming

In logic programming, you define facts and rules. The language works out the answer based on those rules.

Example idea:

Fact: Ram is a parent of Sita.
Rule: If X is a parent of Y, then Y is a child of X.

The system can infer: “Sita is a child of Ram.”

Main example: Prolog
Useful for: rule engines, expert systems, reasoning problems, AI-related logic
You describe what is true or what you want, rather than every exact step to perform.

6. Declarative programming

Declarative programming says what result you want, not necessarily every step for producing it.

Example in SQL:

SELECT name FROM students WHERE marks > 80;

You do not tell the database how to search every row internally. You only declare the result you need.

Common examples: SQL, HTML, CSS, Prolog
Useful for: databases, web page structure, UI styles
HTML describes the content structure; CSS describes how it should look

Compiled vs interpreted

Languages can also be grouped by how the computer runs them.

Type	How it runs	Examples
Compiled	The whole program is translated into machine code before running	C, C++, Go, Rust
Interpreted	Code is generally executed by an interpreter/runtime while the program runs	JavaScript, Python
Hybrid	Code is compiled to an intermediate form, then run by a virtual machine/runtime	Java, C#

Reference:

FOSS

Raja B — Tue, 28 Jul 2026 08:13:45 +0000

TOSS Conf 2026

I attended TOSSConf'26 for three days — 23rd, 24th, and 25th.

* Day 1: Hackathon
* Day 2: Workshops
* Day 3: Open Source Communities

Overall, it was a really great experience for me. 

I met many new people and had the opportunity 
to listen to their experiences. 

I could not understand everything that was discussed, 

but I understood some of the concepts and learned many new things.

I also spoke with many new people. 

Everyone responded to me very kindly and positively. 

The members of the open-source communities were also 
very friendly and supportive.

Many of the people who attended 
the event shared their experiences, 
especially as beginners and as experienced contributors. 

I went there to learn, listen, and gain knowledge, 
and I came back with a lot of new experiences 
and inspiration.

It was a great learning experience, 

and I am happy that I attended TOSSConf'26.

Basic Knowledge

23 ஜூலை 2026

NEET / தேர்வு வினாத்தாள் கசிவு தொடர்பான பிரச்சினை மற்றும் மாணவர் போராட்டங்கள் முக்கிய செய்தியாக இருந்தன

24 July 2026

$1 ≈ ₹96.70 → ரூபாய் மதிப்பு டாலருக்கு எதிராக சரிந்தது

React

Raja B — Sun, 26 Jul 2026 15:18:23 +0000

API

Raja B — Sun, 26 Jul 2026 15:06:30 +0000

API (Application Programming Interface) and how a React frontend communicates with a Java/Spring Boot backend and a database.

Example: Student Management App

Suppose your React page has a student list

1. GET → Get student data

React displays:

ID   Name    Course
1    Raja    Java
2    Arun    Python

2. POST → Add new student

{
  "name": "Raja",
  "course": "Java"
}

3. PUT → Update student

4. DELETE → Delete student

API is like a bridge between React and Spring Boot

Promise

Raja B — Sun, 26 Jul 2026 14:51:57 +0000

A Promise in JavaScript is an object that represents the future result of an asynchronous operation, like fetching data, waiting for a timer, or reading a file.

It can be in one of three states: pending, fulfilled, or rejected.

new Promise(...) creates a new promise
res means resolve, rej means reject
rej() makes the promise fail
.then() runs only when the promise is fulfilled
.catch() runs when the promise is rejected

Analysis() represents an analysis operation that takes 3 seconds. After the analysis finishes, res() tells JavaScript: "The work is completed successfully."
This waits for 3000 milliseconds = 3 seconds.

Reference

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises...

Math JS

Raja B — Sun, 26 Jul 2026 13:08:38 +0000

In JavaScript, Math is a built-in object that gives you common math constants

And functions like rounding, square root, power, and random numbers.

It is not a normal object you create with new;

you use it directly like Math.PI or Math.sqrt(25)

Simple idea

Math.PI gives the value of pi
Math.round(4.6) gives 5
Math.floor(4.9) gives 4
Math.ceil(4.1) gives 5
Math.sqrt(25) gives 5
Math.pow(2, 3) gives 8
Math.random() gives a random decimal between 0 and 1

Example

Reference:

https://www.w3schools.com/js/js_math.asp

SDLC

Raja B — Tue, 21 Jul 2026 08:08:27 +0000

SDLC means Software Development Life Cycle. It is a step-by-step process used to plan, build, test, deploy, and maintain software so the final product is reliable and meets user needs

Main phases

Planning / Requirement analysis: understand what the software should do and what users need
Design: decide the structure, architecture, database, and UI flow
Development: write the actual code
Testing: find and fix bugs before release
Deployment: release the software to users
Maintenance: fix issues, improve features, and update the software over time

Simple meaning

You can think of SDLC like building a house: first you plan, then you draw the design, then you build, inspect, hand it over, and keep repairing or improving it later

Explanation

SDLC na software-a step by step-a develop panna use pannura process. Requirements collect pannitu, design panni, code ezhuthi, test panni, deploy panni, apram maintain pannuvanga

Why it matters

SDLC helps teams work in an organized way, reduce mistakes, and deliver software on time with better quality

DOM

Raja B — Tue, 21 Jul 2026 07:54:40 +0000

The DOM in JavaScript means the Document Object Model. It is the browser’s tree-like representation of an HTML page, and JavaScript uses it to read, change, add, or remove elements on the page

Simple idea

Think of HTML as the page structure, and the DOM as the live version of that page inside the browser. JavaScript talks to the DOM to make websites interactive, such as changing text, styles, or reacting to clicks

<p id="demo">Hello</p>
<button onclick="changeText()">Click</button>

<script>
function changeText() {
  document.getElementById("demo").innerHTML = "Hi Raja!";
}
</script>

Here, document.getElementById("demo") finds the paragraph, and innerHTML changes its content

What you can do with DOM

Select elements
Change text or HTML
Update CSS styles
Add or remove elements
Handle events like click, input, or submit

Reference:

https://www.w3schools.com/js/js_htmldom.asp

React

Raja B — Tue, 14 Jul 2026 07:44:20 +0000

What is React?

React is a JavaScript library used to build user interfaces (UI) for websites and web applications.

It helps developers create fast, interactive, and reusable web pages.

Created by: Meta (Facebook)

Example websites that use React:

Facebook
Instagram
Netflix
WhatsApp Web

Why do we use React?

Without React:

We write lots of JavaScript
Updating the page is difficult
Code becomes large

With React:

Code is shorter
Easy to manage
Faster updates
Reuse the same code many times

What is a Component?

A Component is a small piece of a webpage

Think of a webpage like a house

House → Webpage
Room → Component

Example:

Web Page

├── Header
├── Menu
├── Profile
├── Products
├── Footer

Each part is a component

Why Components?

Instead of writing the same code again and again, we create it once and reuse it

Example:

<Button />

<Button />

<Button />

One Button component can be used many times

CODE on JVM

Raja B — Sun, 12 Jul 2026 07:50:49 +0000

My Experience at Code on JVM Chennai

Recently, I attended the Code on JVM Chennai meetup. It was a new experience for me, and I learned many valuable things from the speakers and the community.

The event featured three inspiring speakers:

Hareesh Rajendran – Founder & CEO of Hayan Tech
Agnel John – Founder & CEO of Error Makes Clever
Kalaivani Mohan – Software Engineer at IBM

Hareesh Rajendran – DSA in Production Speak
Agnel John – Uncovering Ideas Worth Building in the AI Era Speak
Kalaivani Mohan – Streaming Large File Downloads in Java

Networking and Learning:

One of the best parts of the meetup was the opportunity to interact with other developers
I met people from different backgrounds, listened to their experiences, and had meaningful conversations
This helped me improve my confidence and understand the importance of networking

I Learned

his meetup helped me realize that technical knowledge alone is not enough
Communication, networking, and continuous learning are equally important
I still have a lot to learn, but every meetup teaches me something new
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      **Thank you, Code on JVM Chennai!!!**
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