DEV Community: Sathish K

Test Question

Sathish K — Sat, 08 Nov 2025 17:22:37 +0000

Different between static and non static variable.
Static variable:
It is can be accessed using the class.
It is the accessed by the static and non static methods.
It is a reduce the amount of the memory used by the program.
It is a existing the entire lifetime of the program.
It is default value is can assigned automatically.

Non static variables:
It is can be accessed using the instance of the class.
It is cannot be accessed by the inside the static variables.
It is not reduce the amount of the memory used by the program.
It is the existing the lifetime of the program.
It's a default value is cannot assigned automatically.

Different between the local and global variables.

Local variable:
Local variable are declared within the block of the code,such as method or function and have limited scope and lifetime. The code is execution only within the block.

Global Variable:
Global variables are declared the program within the outside of the any function and can be accessed from any part of the program, persisting throughout is execution.

Different between the method and constructor.
Method:
A method must have a return type.
A method is a collection of the statement which return a value upon its execution.
A method cannot create object run to with automatically.
Same method name with different parameters
A method is consisted of java code to the executed.
Constructor:
A constructor doesn't have a return type.
A constructor is a block of code that can initialize a newly object to create.
A constructor can be create a object is run to with automatically.
Same Constructor name with different parameter list.
A constructor can be used to initialize an object.

Constructor

Sathish K — Sat, 08 Nov 2025 17:03:48 +0000

What is the use of constructor and how to create constructor?
A constructor use is to initialize a new object of the class when it is created, ensuring it attributes have a valid state, often by setting the default or user defined values.To be create a same name of a class and no return type. It is a automatically called when you be new keyword to instantiate the object.

What is constructor overloading ?
A constructor overloading is the techique in Java is feature is allowed when a class can multiple constructor with same class name with different parameters is called as constructor overloading.

OOP- Object Oriented Programming Language

Sathish K — Fri, 07 Nov 2025 17:32:19 +0000

Why is study OOP ?
Studying the OOp is important because it create the more organized, secure, reusable code, which make the software development is faster, easier to maintain and more efficient.

What is Platform independent ?

Primitive Data Type, class and object, OOPS in Java

Sathish K — Tue, 14 Oct 2025 18:00:19 +0000

*What is primitive datatype ? *
In Java, primitive data type is a fundamental building blocks storing and manipulating data values. They are the predefined langauage and are not considers the objects.

Types of primitive data types

bytes
short
int
long
float
double
char
boolean

What is OOPs in Java ?
OOP- Object Oriented Programming language
In Java is a programming paradigm based on the concept of objects,classes. It's aims is structure software program in a way of real world entities and their interaction, promoting code reusability,modularity and maintainability.

What is Class in Java ?
In Java, a class serves as a blueprint or a template for creating the objects. It is fundamental concept in OOP and define the structure and behavior that objects of that class will posses.

What the Object in Java ?
In Java , an object is a fundamental concept in OOP and represents a real-world entity or a component within a program.It is an instance of a class.

JDK, JVM, JRE and JIT

Sathish K — Tue, 14 Oct 2025 17:21:38 +0000

What is JDK ?
JDK- Java Development Kit
JDK is a software development environment used to develop java application.Its includes the Java Runtime Environment(JRE) to run the program and also contains tools like the javac compiler and debugger to write,compile and debug code.

What is JVM ?
JVM- Java Virtual Machine
The Java Virtual Machine(JVM) is that enables a computer to run the java program,as well as program written in the other language that are compiled to java bytecode.It is a core of component of Java Runtime Environment and responsible for java "Write Once, Run Anywhere" (WORA) capability.

What is the JRE ?
JRE- Java Runtime Environment
The Java Runtime Environment is a software package to provides the necessary components to run the java program.

What is JIT ?
JIT- Just-In-Time
It is a crucial component in Java Runtime Environment(JRE)
and plays a significant role in optimizing the performance of the java application during execution code.

Java Introduction

Sathish K — Mon, 13 Oct 2025 17:13:18 +0000

What is Java ?
Java is a high-level programming language.
Java is a (oops) object-oriented programming language.
Java is a open source platform.
And platform independence that power of billion devices and application worldwide from enterprise software to mobile apps.
Its original name is a Oak in 1992.
The team at Sun Microsystems that developed the language.

**Syntax:**
public static void main(String[]args){

}

Who is the father of Java program ?
James Gosling is the father of Java programm in 1995.

What is a Platform independent ?

Platform independent in java means a program can be run in any operating system (OS) (likes windows,linux,macOS) without needing to be changed or recompiler.

What is the compiler ?
In Java, a compiler is a program that translates human-readable Java source code into platform-independent Java bytecode.

What is the bytecode ?

Bytecode in Java is an intermediate, low-level code generated by the Java compiler (javac) when it compiles a Java source file (with a .java extension). This compiled code is stored in files with a .class extension.

What is interpreter ?
The interpreter reads and executes the bytecode instructions line by line, translating them into machine-specific instructions that the underlying operating system and hardware can understand and execute. This happens dynamically at runtime.

React.js Question 1

Sathish K — Tue, 07 Oct 2025 17:47:54 +0000

1.What is the difference between a functional component and a class component in React?
Functional component:
These are JavaScript function that accept the props as an arguments and return the JSX with the introduction of React Hooks manage the state and lifecycle methods.Its arrow function declaration.

Class component:
These are ES6 classes that extend the react component and include a render() method that return the JSX.

2.How does JSX work internally? Why do we need it instead of plain JavaScript?
The internal process of converting JSX into valid JavaScript involves a transpilation step, typically handled by a tool like babel.
Step of JSX.
Transpilation.
Element Creation.
Virtual DOM.
JSX is not a requirement to use react but if offers significant advantage that makes it the preferred method for most developers.React code using only React.createElement() calls.

3.What is virtual DOM and how does React we it for rendering ?
The Virtual DOM (VDOM) is a lightweight in memory representation of the actual DOM.It is a JavaScript object that mirror the structure of real DOM, including element ,attributes and their children.
Uses:
Initial Render,State or props change,Diffing,Batch update and Real DOM.

4.Explain Props vs State with an example.
Props:
Props(Properties) are the data passed down from a parent to a child components acting like arguments to a function and are generally read-only.

State:
State is a internal to a component,representing data that can change overtime within that component and is managed internally often using hooks like useState.

5.What is lifting state up in React?
Lifting state up is a React pattern where you move shared state from child component to their closet common parent.This allows multiple child components to communicate and stay in sync via the shared state in the parent.

UseState in React.js

Sathish K — Wed, 01 Oct 2025 17:24:40 +0000

What is UseState ?
The UseState is the hooks in React.js. It is the fundamental hook is allow to functional components to manage and update the internal state.It is a inbuilt function.Its add to state variables to functional components.

Syntax:

const[state,setState]=usestate(0)

Example:

import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0); // Initialize count to 0

  const increment = () => {
    setCount(prevCount => prevCount + 1); // Update count based on previous state
  };

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={increment}>Increment</button>
    </div>
  );
}

export default Counter;

JSON

Sathish K — Mon, 22 Sep 2025 16:59:14 +0000

What is a JSON ?
JSON- JavaScript Object Notation.
A JSON file is a contains structured text in JavaScript Object Notation(JSON)format,a human readable,text-based format for storing
and transmitting data,primarily used for data exchange between a web server and a client.
How JSON Files Store Data ?
JSON files contain structured data in two primary forms:

Objects: Collections of unordered key-value pairs, enclosed in curly braces {}.

Arrays: Ordered lists of values, enclosed in square brackets [].

what are the uses of JSON ?
Data Exchange.
API.
Configuration file.

Why JSON is Popular ?
Simplicity.
Lightweight.
Wide Compatibility.

What is the React.js,JavaScript and JavaScript XML

Sathish K — Wed, 10 Sep 2025 16:23:30 +0000

What is the React.js ?
React is a library for building a user interfaces and open source platform.Its used for UI components based.The facebook and meta is created and maintain the React.
It is defined as the single page application.It is a declarative,efficient and flexible in JavaScript.when virtual DOM,which is a ligth weight memory.React is a faster and improve the performance.
Drawback.
1.Learning Curve
2.JSX is complexity
3.It is only used the library

What is the JS ?
JS- JavaScript is a programming language.It is a general-purpose scripting language primarily used to web development to add the interactivity and dynamic behavior to websites. It can be executed the directly web browser.

let dev= Hello;
console.log(dev);

What is a JSX ?
JSX-JavaScript XML is a syntax extension for JavaScript. It is allow the developer to write HTML like a code directly within JavaScript files. JSX is commonly used to liberies like React to describe the structure of user interface in a declarative way.
It is used to define the UI components.

let element=<h1>Hello</h2>;

NPM,NPX,CRA and VITE in JavaScript.

Sathish K — Wed, 10 Sep 2025 16:03:14 +0000

What is NPM ?
NPM- Node Package Manage.
It is a world largest software libary.
It is open source the developers are use this software and run script.
It is a managing the dependencies your project.

git commands:
sudo apt install npm
npx create-react-app name
cd name
npm start

vite
npm create vite@latest
project name
react .js
javascript
cd name
npm start

What is NPX ?
NPX- Node Package eXecutes
It is a command line utility the bundled with NPM.
Its verision is 5.2.0.
NPX is primary purpose for the allow of the developer executes the node.js package is directly npm.
Its need for prior global or local installation.

What is the CRA ?
CRA- Create React App
Create React App is the command line tools offically.
The react team are help to set up a new react projects with good default configuration.

What is the VITE ?
VITE is a modern javascript built up the designed tools help the faster and lerner development the experience for web project.

NPM,NPX,CRA and VITE in JavaScript.

Sathish K — Fri, 05 Sep 2025 18:06:24 +0000

What is the CRA ?
CRA- Create React App
Create React App is the command line tools offically.
The react team are help to set up a new react projects with good default configuration.

What is the VITE ?
VITE is a modern javascript built up the designed tools help the faster and learner development the experience for web project.