DEV Community: muthukumarasamy thangavel

Java Object

muthukumarasamy thangavel — Fri, 25 Sep 2026 04:07:31 +0000

What is Object?
** Package name:java.lang.Object**
--> Run time memory allocation.
-->Class Object is the root of the class hierarchy.
-->Every class has Object as a superclass.
--> All objects, including arrays, implement the methods of this class.
-->Everything in Java is associated with classes and objects, along with its attributes and methods.

Example:

 SuperMarket product2 = new  SuperMarket();
 object creation statement

Variables:
-->Variables are containers for storing data values.
-->Variables in Java are used to store data values during program execution. Each variable is associated with a specific data type that defines the kind of value it can hold. Variables help in performing operations, storing user input, and managing data in a program.

1.Local variable -Non static variable
2.Instance variable - Non static variable
3.Global variable -Static variable

Local variable:
-->A variable defined within a block, method, or constructor is referred to as a local variable.
-->Its stored in stack memory.
-->We first need to initialize a local variable before using it within its scope.
-->We first need to initialize a local variable before using it within its scope.
Example:

public static void main(String[] args){
int  age = 20;
String  name = "kumar";
}

Instance variable:

-->Instance variables are known as non-static variables and are declared in a class outside of any method, constructor, or block.
-->Instance variables are created when an object is instantiated and destroyed when the object is destroyed.
-->Can have access specifiers; default access is used if none is specified.
-->Accessed only through objects of the class.
-->Instance Variables can be initialized using constructors or instance blocks.

public class Student{
//Instance Variable
String student_name = "Selvakumar";
int toatal_mark = 420;
    public static void main(String[] args){
        //Local variable 
        int  age = 20;
        String  name = "kumar";
}
}

Static Variable(or) Global variable :
-->Static variables in Java are variables declared with the static keyword inside a class but outside any method.
-->They are shared among all objects of the class and exist for the entire lifetime of the program.
-->There is only one copy of a static variable for the entire class, and all objects share it.
-->Static variable are created at program start and destroyed when the program ends.

public class Student{
//Static variable  with static keyword
static  String  collge_ name = "Excel Eng college";
static int  code = 837;
//Instance Variable
String student_name = "Selvakumar";
int toatal_mark = 420;
    public static void main(String[] args){
        //Local variable 
        int  age = 20;
        String  name = "kumar";
}
}

Java OOPS Basic and Class

muthukumarasamy thangavel — Tue, 22 Sep 2026 14:07:22 +0000

what is oops concept in java?
*oops --> Object Oriented Programming Structure *
--> OOPS is ideal for building scalable, reusable, and maintainable code.
-->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.

-->OOPS provides a clear structure for the programs.
-->OOPS 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.

OOPS:
*Class
*Object
*Inheritance
*Polymorphism
*Abstraction
*Encapsulation

*Class *
-->Create Class start with capital letter.
--> A class is a blueprint or prototype from which objects are created. This section defines a class that models the state and behavior of a real-world object.
--> class is a collections of objects and methods.
--> class space is not allowed except($,_) only allowed.
--> class are allowed numbers (middle and end only ) not allowed start.

Data Types:
*Byte (1byte)
*Short (2 byte)
*int (4 byte)
*Long (8 byte)
*float (4 byte)
*Double (8byte)
*Char ('A' only one character)
*boolean (True (or) False)

Java is define two data types:
1.primitive
2.Non-primitive

primitive:
-int
-short
-byte
-long
-double
-boolean
-char

Non-primitive:
-String
-Array

Java Induction

muthukumarasamy thangavel — Mon, 21 Sep 2026 14:41:31 +0000

what is Java?
-->simple programming language.
--> platform independent.
-->OOPS -> object oriented programming structure.
--> Java is a widely used programming language for building web, desktop, mobile, and enterprise applications.
-->Secure and robust with strong memory management.

java simply called as JDK--> Java Development kit

JDK contains the JRE and JVM

JDK:
It is called as java compiler.
Its compiles the source file in to byte code.
ex: Home.java convert into Home.class
in terminal run command javac Home.java run this command
automatically create the Home.class file javac in c means Compiler
onece the compile the program run anywhere

JRE (Java Runtime Environment)
-->The Java Runtime Environment (JRE) traditionally refers to the components required to run a Java application.

-->It consists primarily of the JVM and the Java runtime libraries.
--> its main component JVM.

-->JRE is a software package that provides Java class libraries, JVM, and other components that are required to run Java applications.

-->JRE is the superset of JVM.

JVM Java Virtual Machine
-->JVM is an abstract machine that enables your computer to run a Java program.

-->When you run the Java program, Java compiler first compiles your Java code to bytecode. Then, the JVM translates bytecode into native machine code (set of instructions that a computer's CPU executes directly).

-->Java is a platform-independent language. It's because when you write Java code, it's ultimately written for JVM but not your physical machine (computer). Since JVM executes the Java bytecode which is platform-independent, Java is platform-independent.

public  class Home{
public static void main (String[]  args){

    System.out.println("Hello java");
}

}

Its compile to the code create the Home.java file

again run the command line java Home program will execute

Python _ String Introdution

muthukumarasamy thangavel — Mon, 07 Sep 2026 04:26:09 +0000

What is String?
->String is immutalble.
->All the languages string is spcial method.
->String in python are surrounded by either single qutation marks, or double qutation marks.
-> In Python more string methods are available.
-> String are commonly used for text handling and manipulation.

Immutable:
->Existing Memory wont get affected. Instead, change will be updated in new memory.
Mutable:
->A mutable value is one that can be changed without creating an entirely new value, in comparison with immutable values.

name = "Muthukumarasamy" #String 
print(type(name))   # its print only the which type <class 'str'>
print(id(name))    # its print memory allocation ID

Output:
     <class 'str'>
     2702430470704

Garbage Collector:
->Unsed memory objects.
->Garbage Collection in Python is an automatic process that handles memory allocation and deallocation, ensuring efficient use of memory.
->In python method gc in this method import th python file
-> Garbage collection mostly used for the OTP verfication.
-> More methods are available.
-> Commomly uesed method are:

gc.enable()
Enable automatic garbage collection.
gc.disable()
Disable automatic garbage collection
gc.isenabled()
Return True if automatic collection is enabled.

name = "Muthukumarasamy"    
print(id(name))            # its unused memory its called by the garbage collection old memory:  2639045886512
name = "T Muthukumarsamy"
print(id(name))           # new Memory allocation its a string  new memory allocation: 2639045890608

String Length:

name = "MuthuKumarasamy"
print(len(name))      # string length calculator
i = 0
while i<len(name):
     print(name[i],end = ' ')
     i+=1

Method overload:
->The @overload decorator allows describing functions and methods that support multiple different combinations of argument types.
->This pattern is used frequently in builtin modules and types.

Examble:

print('spam, spam, spam'.find('sp'))

print('spam, sdam, spam'.find('sp', 5))

class calculater:
    def add (self, a , b=0):
        return a+b

calc = calculater()
print(calc.add(5)) 
print(calc.add(5,10))

Software Testing

muthukumarasamy thangavel — Mon, 17 Aug 2026 03:50:21 +0000

Today we are discuss testing topic how to behave testing team was discussed.
Testing:
The Process of software the evaluating software application to verify that works as expected and meets specified requirements. its helps identify the defects, errors and missing functionalities before the software delivered the users.

Manual Testing:
Human eye captures more defects.
everything cannot be automated like captcha, image, animation, video ..,

There are the two types of the software testing

1.Functional testing

Non-Functional testing

Functional Testing:
Manual testing (Testing the functionalities manually)
Automation testing (Testing the functionalities by automation by using the the tools/scripts)
Web services Testing (validating request and response) - its called by API Testing
Non-Functional Testing:
Checking the non-functional aspects of the application

ISTQB--> International Software Testing Qualifications Board

Today write the small test scenario:

POSTGRESQL Induction

muthukumarasamy thangavel — Fri, 14 Aug 2026 13:54:13 +0000

POSTGESQL:
postgreSQL is powerful open source object-relational database system.
PostgreSQL has earned a strong reputation for its proven architecture, reliability, data integrity, robust feature set, extensibility, and the dedication of the open source community behind the software to consistently deliver performant and innovative solutions.
PostgreSQL runs on all major operating systems.

why postgreSQL:
PostgreSQL comes with many features aimed to help developers build applications.
Administrators to protect data integrity and build fault-tolerant environments, and help you manage your data no matter how big or small the dataset.
Data Type
Data integrity
Concurrency
Security
Reliability

Data Types

Primitives: Integer, Numeric, String, Boolean
Structured: Date/Time, Array, Range / Multirange, UUID
Document: JSON/JSONB, XML, Key-value (H store)
Geometry: Point, Line, Circle, Polygon
Customizations: Composite, Custom Types

postgres open the Linux machine:

 sudo -i -u postgres
[sudo] password for muthukumarasamy:       
postgres@muthukumarasamy-HP-Pavilion-15-Notebook-PC:~$ psql
psql (16.14 (Ubuntu 16.14-0ubuntu0.24.04.1))
Type "help" for help.

postgres=#

postgresql is the not for the case sensitive.

PSQL Shortcut:
\h ---> help
\c---> connect DB
\d ---> Details
\r ---> reset
\l ---> list
esc+shift+:+Q ----> Quit

DBMS---> Database management systems
RDBMS ---> Relational Database Management systems

Database management systems
A Database Management System (DBMS) is software used to manage data from a database. It acts as an interface between the database and end users or applications, ensuring data is consistently organised, easily accessible, and secure.

A database is a structured collection of data that is stored in an electronic device. The data can be text, video, image, or any other format.
A relational database stores data in the form of tables, and a NoSQL database stores data in the form of key-value pairs.
A DBMS is a software that allows to create, update, and retrieval of data in an organized way. It also provides security to the database.
Examples of relational DBMS are MySQL, Oracle, Microsoft SQL Server, PostgreSQL, and Snowflake.
Examples of NoSQL DBMS are MongoDB, Cassandra, DynamoDB, and Redis.

RDBMS ---> Relational Database Management systems:

RDBMS stands for Relational Database Management Systems. A database is an organized collection of data stored in a computer system and usually controlled by a database management system (DBMS). It is a program that allows us to create, delete, and update a relational database.

Data is organized in a structured, tabular format
Tables are related to each other using keys
Supports easy and powerful query execution
Can handle large volumes of data efficiently

Constructor in JS

muthukumarasamy thangavel — Wed, 15 Jul 2026 04:26:21 +0000

constructor:
In js constructor is an a special function or method used to create and initialize object instances.
called automatically when created object.
constructor name should be start with upper case. (Pascal notation )
this refer to current object.
Object() can be called with or without new, but sometimes with different effects. See Return value.
Inside a constructor, this -->refers to the newly created object (or) current object.
Ex:
const function name = new Object();

const emp1 = new Person("muthu",27,"indain","india","vkp@gmail.com");

function Person(name,age,nationality,country,mailid){
console.log(this.name =name);
console.log(this.age = age);
console.log(this.nationality = nationality);
console.log(this.country = country);
console.log(this.mailid = mailid);

Javascript Objects

muthukumarasamy thangavel — Tue, 14 Jul 2026 08:32:00 +0000

Objects
Objects is contains the in formations
objects contains run time memory allocations
create method and set of actions the same as the objects
ex:
name:"Samsung"
(key : value )
Objects is the Key and Value pair

objects most important concept of the java script

Properties:
objects can be changed added and deleted

Methods:
method are actions can be performed on objects

object call as the method name easy to access

JavaScript Operators

muthukumarasamy thangavel — Mon, 06 Jul 2026 13:21:18 +0000

Today we have discuss the operators and also some example task

Different types of Operators
Arithmetic operators
Assignment operators
Comparison operators
logical operators

Arithmetic operators:
Addition - +
Subtraction - -
Multiplication -*
Increment - ++ (pre &post increment)
Decrement - -- (pre &post Decrement)

Assignment Operator: =
this operator is assign in value to variable

In javascript any number add into the string, the number is automatically change in to the string type.
Example:
50 + 8 = 58
7 + "7" = "77"
in javascript subtraction value add in the string value it subtract to value but you will subtract to the letters NaN (Not a Null)
you will get NaN it means (Numeric datatype)
Example:
10-"2"=8
"mohan"-10 =NaN

Multiplication:
In javascript is multiplaction add in to string value is multiply but string letter NaN so same as subtraction
Example:
2*5 = 10
"ram"*10 =NaN

Assignment operators:
All assign the value to the variable using in this o operator
let a = 5
let b = 6

Comparison operator:
In this operator to the value
Ex:
5==5

Increment& decrement Operator:
in this two types pre & post increment and pre & post Decrement operator
ex:
pre and post increment
pre;
++3 = 4
++6 =7
post:
2++
6++
pre and post decrement:
ex:
pre:
--8
--5
post:
9--
5--

SDLC -SOFTWARE LIFE CYCLE DEVELOPMENT

muthukumarasamy thangavel — Sat, 04 Jul 2026 13:20:59 +0000

today we are discussed SDLC (software Life Cycle Development)
how its work and also

Requirement Analysis gathering
Analysis
Planning
Development
Testing - STLC
Deployment
Operations and maintenance

1.Requirement Analysis:
Role play:Business Analyst
client to meet and gathering the application requirement.
writing the plain language its called BRD.
common man understand documentation the language no technical terms.
Once collect document after the walk though section.
Discuss with project manger.
planning the requirement resource,software,hardware,duration of the project,sign off project and how many months the development and testing environment.
which methodology follow now follow the only one agile methodology
form the team Agile methodology.
how many sprint done the first phase.

Design:
All requirement understand Design will start the UI/UX front-end design start. software architecture user interface will done quickly.
its the first phase of the project.

Development:
development team design finish the code will start.
development team work with dev environment.
once done first phase of the code change to the test environment

Testing:
Before that code receive testers work STLC model
Business analyst work same time will tester also work the same procedure this model:
Requirement analysis
Test planning
Test Design
Test Execution
sign off

Requirement analysis:
Understand the BR document
Clarification and doubts logs though session
identify test types to be performed
get application access

Test Planning:
preparation the test plan document for various of testing
test tool selection
Automation who will when will do
manual who will do when will do
resource planning

Test Design:
test scenarios,test case,automation script,RTM (requirement tracability matrix)
create test data
review the test case peer or lead
get approval

Test Execution:
execute the test cases as per the plan
Document test result and log defects for fail cases
track defects to closure
retest the defect fixes
Execution result defect log

Sign off:
evaluate the cycle completion
prepare test closure reports
test result analysis

Every phases the entry and exit criteria.

Defect life cycle (DLC):
once defect fix the it will automatically work
New:
when the defect the found the and posted for the first time
Assigned :
once defect posted the testing team will assign the dev team
open:
once the developer opens the bug and work on fix it
Fixed:
when developer fixed the bug with appropriate codes
Pending retest:
When the tester retesting the whether the bug it will be moved on the testing team
Retest:
when the retesting whether the bug raised was fixed or not.
Verified :
If the tester confirms the bug fixed
Reopen :
if the tester confirms that bug is not found the same defect again it will moved to assigned stage and flow continuous

Closed:once the tester verified the bug is fixed then defect raised will be closed
Duplicate:
if the bug is already by some one and if it is raised again will be duplicate.
Rejected/ Not a bug:
when the developer feels that the bug is not genuine.
Deferred:
This bug which developer feels that it can be fixed later the upcoming sprints.

JavaScript

muthukumarasamy thangavel — Mon, 29 Jun 2026 15:04:18 +0000

n May 1995, Brendan Eich created JavaScript, a programming language, in just ten days. Initially developed to enhance interactivity on websites, it was designed to add dynamic features to static HTML pages, primarily for client-side development.

Creation of JavaScript

In 1995 Netscape Communications Corporation needed a way to make web pages more interactive and dynamic.
Brendan Eich was hired by Netscape to develop a new scripting language for this purpose.
The language was initially called Mocha and later changed to LiveScript.
In December 1995, Live Script was renamed JavaScript, partly to capitalize on the growing popularity of the programming language Java.
JavaScript was designed to be lightweight, interpreted, and primarily used for client-side scripting to manipulate web page elements in real-time.
The language was quickly integrated into Netscape Navigator, the leading browser of the time, marking the beginning of JavaScript’s role in web development

JavaScript and ECMAScript

In 1996 javaScript was submitted to ECMA International, a standardization organization, for approval.
This submission led to the creation of the ECMAScript standard, which outlined the specifications for the language.
The first edition of ECMAScript was published as ECMAScript 1 in 1997.
The initial version of JavaScript was basic and lacked many modern features we now use.
Although limited in functionality, the first version of JavaScript was still revolutionary for web development at the time

JavaScript’s Growth (1997-2005)

During the late 1990s and early 2000s, JavaScript's capabilities started to evolve, and more browsers began supporting it.

2005:
The introduction of AJAX in web applications such as Gmail, allowing for faster, more dynamic web experiences.

2006:
jQuery, a popular JavaScript library, was created by John Resig. It simplified DOM manipulation and event handling, gaining massive popularity.

2008:
Google Chrome was released, with its JavaScript engine, V8, making JavaScript faster and more efficient.

Modern JavaScript (2009-Present)

JavaScript evolved to handle both client-side and server-side development, expanding its capabilities significantly.

React-2013:
Component-based architecture, virtual DOM for better performance.

Angular-2010
Two-way data binding, dependency injection, MVC architecture.

Vue.js-2014:
Lightweight, flexible, and easy to integrate into existing projects.

The Future of JavaScript
JavaScript continues to evolve and adapt to new technologies.
Upcoming trends include the growth of WebAssembly, which allows running code written in other languages alongside JavaScript in the browser.
Serverless computing is gaining traction, allowing developers to build applications without managing servers, with JavaScript playing a key role.
Machine learning is being integrated into JavaScript, enabling the development of intelligent web applications.
TypeScript, a statically typed superset of JavaScript, is becoming increasingly popular, offering more structure and reducing errors in large projects.
The future of JavaScript looks promising with more robust tools and features to help developers build better applications
**
Major Updates and Modern JavaScript**

** ES4*: Proposed major changes that ultimately led to significant debate and were not adopted, laying the groundwork for future developments instead.
* ES5*: Released in December 2009, ES5 introduced JSON support, strict mode, and getters and setters, among other improvements, marking a significant update widely adopted by modern browsers.
**ES6/ES2015: A landmark update introduced in June 2015, it brought major syntax improvements such as classes, modules, template literals, arrow functions, promises, and many other language enhancements.
**ES2016+*: From 2016 onwards, the ECMAScript standard adopted an annual release cycle, introducing new features in smaller, more manageable updates. Notable features include async/await (ES2017), spread/rest operators (ES2018), optional chaining, and nullish coalescing (ES2020), among others

JavaScript Data Types

muthukumarasamy thangavel — Mon, 29 Jun 2026 15:03:44 +0000

Number-A number representing a numeric value
Bigint-A number representing a large integer
String-A text of characters enclosed in quotes
Boolean-A data type representing true or false

They are the two types of data types:
Primitive Datatype
Non-primitive Datatype

Primitive Datatype:
Numeric Type:
Number
Bigint
Non Numeric Type:
String
boolean
undefined
null
symbol