DEV Community: Praveen

Architecture of java,node.js, python

Praveen — Fri, 26 Jun 2026 07:27:53 +0000

Components of Java Architecture
Java architecture consists of three main components and those are JRE(Java Runtime Environment), JDK(Java Development Kit), and JVM(Java Virtual Machine).

Java Runtime Environment(JRE)
Java programs can run in a runtime environment created by the JRE software. The Java Runtime Environment (JRE) is a disk-based system that mixes Java code with necessary libraries. Finally, the Java Virtual Machine (JVM) begins to run the Java code. The Java Runtime Environment (JRE) contains all of the libraries and software required to run Java programs. Although JRE is included in the JDK, it is also available for download individually.

Java Development Kit(JDK)
It’s a Java application and applet development environment. JRE, a compiler, an interpreter or loader, and a number of development tools are all included in the Java Development Kit. Now we will walk through these development tools which come along with JDK:

Java(loader/executor): responsible for launching Java applications
javac(compiler): It is responsible for compilation of java programs
Javadoc: provides support for generation of API documentation
Jar: responsible for creating and managing all JAR files.
Java Virtual Machine(JVM)
WORA is Java’s most important feature. Write Once, Run Anywhere is an acronym for WORA. We may develop our code once and utilize it anywhere and on any operating system, according to the feature. Due to the Java Virtual Machine, our Java software can execute on any platform. It is a Java platform component that provides us with a platform in which we can run Java programs. The basic job of the JVM is to transform byte code into machine code. On the whole, JVM performs these functions – loads and verifies the code and then executes the code, and enables the runtime environment.

Node.js Architecture
Client Request
↓
Event Loop
↓
Node.js APIs
↓
libuv (Thread Pool / OS)
↓
Callback Queue
↓
Response Sent

Python Architecture
Python follows an interpreter-based architecture, where source code is first compiled into bytecode and then executed by the Python Virtual Machine (PVM).

Python Source Code (.py)
↓
Python Compiler
↓
Bytecode (.pyc)
↓
Python Virtual Machine (PVM)
↓
Operating System

Paradigms in programming

Praveen — Thu, 25 Jun 2026 07:15:22 +0000

A programming paradigm is a method or style of solving problems using a programming language. It provides a structured approach and set of principles that guide how programs are designed and implemented.

Different programming paradigms use different techniques and strategies to solve software development problems efficiently.
A programming language may support one or more paradigms, allowing developers to choose the best approach based on project requirements.
Apart from the variety of programming languages available, there are several paradigms that address different demands and challenges in software development. These paradigms are discussed below
Imperative Programming Paradigm

Procedural programming paradigm:
Object oriented programming
Parallel processing approach

. Declarative programming paradigm

Logic programming paradigms
Functional programming paradigms
Database/Data driven programming approach

Java-object oriented programming language

Praveen — Thu, 25 Jun 2026 07:11:10 +0000

Java - What is OOP?
OOP stands for Object-Oriented Programming.

Procedural programming is about writing procedures or methods that perform operations on the data, while object-oriented programming is about creating objects that contain both data and methods.

Object-oriented programming has several advantages over procedural programming:

OOP is faster and easier to execute
OOP provides a clear structure for the programs
OOP helps to keep the Java code DRY "Don't Repeat Yourself", and makes the code easier to maintain, modify and debug
OOP makes it possible to create full reusable applications with less code and shorter development time
Java - What are Classes and Objects?
Classes and objects are the two main aspects of object-oriented programming.

Look at the following illustration to see the difference between class and objects:

class
Fruit

objects
Apple

Banana

Mango

Another example:

class
Car

objects
Volvo

Audi

Toyota
inheritance inheritance

Inheritance in Java is a core OOP concept that allows a class to acquire properties and behaviors from another class. It helps in creating a new class from an existing class, promoting code reusability and better organization.

A subclass can reuse the fields and methods of the parent class without rewriting the code
A subclass can add its own fields and methods or modify existing ones to extend functionality.

Errors in Java program

Praveen — Thu, 25 Jun 2026 04:42:33 +0000

class game is public,should be declared in a file name Game.java
public class Game

error -2

semicolon is should be at the end

Error-3-6

Error -7

System case sensitive

Error -8

I
String error

UseMemo in react

Praveen — Wed, 10 Jun 2026 05:17:14 +0000

The React useMemo Hook returns a memoized value.

Think of memoization as caching a value so that it does not need to be recalculated.

The useMemo Hook only runs when one of its dependencies update.

This can improve performance.

The useMemo and useCallback Hooks are similar:

useMemo returns a memoized value.

useCallback returns a memoized function.

Learn more about useCallback in the useCallback chapter.

Without useMemo
The useMemo Hook can be used to keep expensive, resource intensive functions from needlessly running.

In this example, we have an expensive function that runs on every render.

When changing the count or adding a todo, you will notice a delay in execution.

useReducer hook in react

Praveen — Fri, 05 Jun 2026 04:15:09 +0000

The useReducer hook is an alternative to the useState hook that is preferred when you have complex state logic. It is useful when the state transitions depend on previous state values or when you need to handle actions that can update the state differently.

Syntax:

const [state, dispatch] = useReducer(reducer, initialState);

reducer: A function that defines how the state should be updated based on the action. It takes two parameters: the current state and the action.

initialState: The initial value of the state.

State The current state returned from the useReducer hook.

dispatch: A function used to send an action to the reducer to update the state

state.count

import React, { useReducer } from 'react';

const counterReducer = (state, action) => {

switch (action.type) {

case 'INCREMENT':

return { count: state.count + 1 };

case 'DECREMENT':

return { count: state.count - 1 };

case 'reset':

return { count:0 };

default:

return state;

}

};

function Counter() {

const [state, dispatch] = useReducer(counterReducer, { count: 0 });

return (

Count: {state.count}

dispatch({ type: 'INCREMENT' })}>Increment

dispatch({ type: 'DECREMENT' })}>Decrement

button onClick={() => dispatch({ type: 'reset' })}>Decrement

);

}

export default Counter;

Closure in javascript

Praveen — Thu, 07 May 2026 07:45:07 +0000

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

INTRODUCTION OF ME

Praveen — Tue, 21 Apr 2026 08:45:49 +0000

Myself praveen
Thank you for giving opportunity introduce myself to you.
Now iam pursuing full stack Java development course.I had a skills
In Html,css and javascript and also done projects in Html,css and I know the basic concepts of javascript .I writing blogs in dev.to related to what I am learned everyday .and also passionate about the video editing doing freelance edits for the clients also.so i taken career as a developer and passion as video editing . that's all thank you

Javascript iteration method

Praveen — Thu, 16 Apr 2026 08:06:26 +0000

For each method
The forEach() method calls a function for each element in an array.
Const marks =[24,35,100,47,55,65]
Marks.forEach(display);
Function display (V);{
Console.log(V);
}
We can able to get value,index,array

For.map method
map() creates a new array from calling a function for every array element.

map() does not execute the function for empty elements.

map() does not change the original array.
Const marks =[100,99,98,96,75];
Marks.map=(display)
Function display (V)
{
Return v+3
}
flat map

The flatMap() method first maps all elements of an array and then creates a new array by flattening the array.
Const products =["car,bike","sofa,bed","shirt,pant"
Console.log (products.map(a=>a.split(","));
Filter
const numbers = [45, 4, 9, 16, 25];
const over18 = numbers.filter(myFunction);

function myFunction(value, index, array) {
return value > 18;
}

Call back function we

Praveen — Wed, 15 Apr 2026 08:02:54 +0000

What is Synchronous JavaScript?
In synchronous programming, operations are performed one after the other, in sequence. So, basically each line of code waits for the previous one to finish before proceeding to the next. This means that the program executes in a predictable, linear order, with each task being completed before the next one starts.

What is Asynchronous JavaScript?
Asynchronous programming, on the other hand, allows multiple tasks to run independently of each other. In asynchronous code, a task can be initiated, and while waiting for it to complete, other tasks can proceed. This non-blocking nature helps improve performance and responsiveness, especially in web applications.

call back function.
Call back function is an passed an argument into Anto another function

Java script is single threaded programming language
JavaScript is traditionally single-threaded because it operates in a single execution context — there is one call stack where functions are pushed and popped as they are executed. In JavaScript, the call stack operates on a LIFO (Last In, First Out) basis, where functions are executed in the order they are pushed onto the stack.

However, just because JavaScript is single-threaded doesn’t mean it’s inefficient or incapable of handling multiple tasks. The secret lies in JavaScript’s ability to handle asynchronous operations using non-blocking features.

Java script array methods

Praveen — Thu, 09 Apr 2026 08:28:16 +0000

1*Array length*

The length property returns the length (size) of an array:

Example
const country = ["India", "pakistan", "Australia", "newzealand"];

let size = country.length;

2*Javascript array tostring*
JavaScript Array toString()
The toString() method returns the elements of an array as a comma separated string.
const fruits = ["Banana", "Orange", "Apple", "Mango"];

let myList = fruits.toString();

3.JavaScript Array at()
Examples
Get the third element of fruits using at():

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fruit = fruits.at(2);

4.JavaScript Array join()

The join() method also joins all array elements into a string.

It behaves just like toString(), but in addition you can specify the separator:

Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.join(" * ");
Result:

Banana * Orange * Apple * Mango

4.JavaScript Array push()
The push() method adds a new element to an array (at the end):

Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");

5.The push() method adds a new element to an array (at the end):

Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");

6.JavaScript Array unshift()
The unshift() method adds a new element to an array (at the beginning), and "unshifts" older elements:

Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon");
7.JavaScript Array delete()
Using delete() leaves undefined holes in the array.

Use pop() or shift() instead.

Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
delete fruits[0];