Forem: SELVAKUMAR R

Chennai to velangiri Hills Trip

SELVAKUMAR R — Wed, 25 Feb 2026 08:24:43 +0000

The trip is start with 3 members from home at time of 7.25 pm in friday evening after getting the pleasing of god we start walk to local railway station for getting train for central railway station chennai. we reached the central railway station at 8.30 pm. In central railway station two team members are waiting with samosa for us. In central railway station we purchase the snacks an food for the trip. Our friend names are Gowtham, Sethu, Elango, Vasu, Prakash, Gowtham brother. Gowtham is buying the chapathi in IRTC chennai central railway station. I can buy the biscuit for friends. sethu buy the kadalai mettai for us. The train for chennai central to coimbator arrived at 10.50 pm . Gowtham and elango went inner to the train to putting the seat for us. After settle in the seat the train start at 11.50 pm. In this time gowtham brother is unable to join with as in central railway station because he stucked in chetpet railway station. He can catch another train to reach the coimbator. we reach the coimbator junction at 6.30 am at saturday. Me, sethu and gowtham roaming in railway station and buy tea for drink. Gowtham brother reached the coimbator railway station at 9.45 am. After that we take bus to gandipuram bus stop to pickup the our friend name jayasurya and gowtham college friend. At 10.30 am we finish the breakfast. After that we went for maruthamalai murugan temple at 11.30 am from gandipuram bus stop. Maruthamalai murugan temple is the mini tracking of velangiri hills . we reach the temple for completing the 700 steps.

After successful dharisanam of murugan temple we reached again gandipuram bus stop to get bus for isha shivan temple.

Collection in Java

SELVAKUMAR R — Wed, 18 Feb 2026 07:50:23 +0000

Collection is the java framework to store and manage the group of objects

It provide the interface and class for managing the objects

Collection interface have two sub interface Listand Set

List interface having the two sub class ArrayListand
LinkedList

Set interface having the three sub class Hashsetand
LinkedHashset and Treeset

Boxing -> Change from Primitive datatype to non primitive datatype

Unboxing -> Change from Non Primitive datatype to primitive datatype

Autoboxing -> java follows this boxing to using datatype

Class and Object

SELVAKUMAR R — Tue, 09 Dec 2025 10:13:15 +0000

Class
-> Class is the blue print to object creation
-> It provide initial value for state (variable) and implementations of behavior (method).

Object:
-> Object is the instance of the class
-> Object is created using new keyword at the run time it allocate the memory in heap

Ex:

ClassName objectName = new ClassName();

Java OOPS Concepts

SELVAKUMAR R — Thu, 04 Dec 2025 06:51:52 +0000

why java use oops concept ?
In java oops concept is used to organize the code, reusability and maintaining the code

OOPS CONCEPT IN JAVA
-> Class
-> Object
-> Inheritance
-> Polymorphism
-> Encapsulation
-> Abstraction

Software Testing

SELVAKUMAR R — Fri, 14 Nov 2025 09:25:37 +0000

Testing:
Releasing the Quality Product

Rules in testing => Expectation output = Actual output

Quality -> Meeting the customer requirement

On Time meeting of the customer with right price

Quality Factors

Reliability (trust)
Stability (Value not change)

Software Quality

Software quality is divided in to two types

System software
Application Software

Variable and Object Creation in Java

SELVAKUMAR R — Fri, 07 Nov 2025 07:51:58 +0000

Variable:

Variable is the named memory location to store the value with datatype

Variable is classified in to two types Local variable and Global variable

Local variable:

Local variables are declared in between the block, method when the block get ends local variable memory is deleted

Ex:

Public class Classroom{
public static void main(string args[]){
String schoolName="Sowdambikaa Matric Hr Sec School";
int Rooms= 24;
System.out.println(schoolName);
System.out.println(Rooms);

}
}

Output:

Sowdambikaa Matric Hr Sec School
24

Global Variable:

Global variables are created inside the class but outside the method to access the variable in another method.

Global Variable is divided in to two types static variable and Non static variable

Static Variable:

Static keyword is used in variable declaration to specifies the class information.

Public class Classroom{
static String schoolName="Sowdambikaa Matric Hr Sec School";
static int Rooms= 24;
public static void main(string args[]){
System.out.println(schoolName);
System.out.println(Rooms);
System.out.println(Classroom.schoolName);
System.out.println(Classroom.Rooms);
}
}

Output:

Sowdambikaa Matric Hr Sec School
24

Non static Variable:

Non Static variable declaration to specifies the Object information.

Non static variable is unable to print directly in the main method if we try to print it throws the error

Ex:

Public class Classroom{
string Name = "Selva";
int age = 24;
public static void main(string args[]){
System.out.println(Name);
System.out.println(age);

}
}

Output:

Error : Non static variable name cannot be referenced from a static context

Object Creation:

Public class Classroom{
string Name = "Selva";
int age = 24;
public static void main(string args[]){
Classroom student = new Classroom();
System.out.println(student.Name);
System.out.println(student.age);

}
}

Output:

Selva
24

Class and Data Types in Java

SELVAKUMAR R — Thu, 06 Nov 2025 15:03:10 +0000

Class:

It is one of the major concept in OOPS concept
It act as container to grouping the object
Without class we can't able to create the object in java program
Class Name first letter must be capital and should be meaningful

Syntax for Class creation:

public class Home
{

}

public- Access Modifier

class - Keyword

Home- It is the class name

While compile the above program it convert in to .class File but while in execution it throw the error Required public static void main(string [] args) because the program start execute from the main method only and also common method for java program inside of the main method we call many method but in java program main method is most important

public class Home{
public static void main(string[] args)
{
System.out.println("Hello world");
}
}

Inside Class Have Data members, Method, Objects, Constructor

*Datatypes: *

In Java Data type is divide in to two types

primitive Datatype (Fixed Memory)
Non primitive datatype (Random Memory)

Primitive Datatype:

In this primitive datatype having 8 different datatype to storing the data

Byte:
1 byte = 8 bit => bit represents the binary (2) so 2 power 8 = 256
in that memory allocated -128 to +127 it is used store the small whole number

Short - 2 byte

int - 4 byte

long - 8 byte it is used to store the long whole number we need to add the L at end of the number to indicate the system this number is long datatype

float - 4 byte it is used to store the floating point value by adding the f at end of the number to indicate the system this is the float datatype

Double - 8 byte

char - 2 byte ' ' single quotes is used to store the single character instead of adding the one more character in single quotes it throughs the error.

Boolean - 1 bit (true or false)

Non primitive Datatype:

In non primitive datatype the values or not stored directly in memory instead store reference

Examble :

Object, class, Array, Interfaces, Strings,

Enums: Define a set of named constants.

enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}

HashMap , HashSet, ArrayList - collections

Array Basics

SELVAKUMAR R — Tue, 04 Nov 2025 02:26:54 +0000

Array is used to Grouping the similar datatype

Array size cannot be defined by datatype

Array is index based because we can get the values from array using index only

Array Maximum length is integer maximum storage size it is applicable for all datatype

Array Minimum length is zero

Examples of Array

1. printing the array value without using the looping concept:

Class Arraypractice{

Public static void main(args[])
{

int[] Marks = {90, 100,79, 84, 98};

System.out.println(Marks[0]);
System.out.println(Marks[1]);
System.out.println(Marks[2]);
System.out.println(Marks[3]);
System.out.println(Marks[4]);

}
}

Output:
90
100
79
84
98

2. Printing the array value using the looping statement:

Class Arraypractice{

Public static void main(args[])
{

int[] Marks = {90, 100,79, 84, 98};

System.out.println(Marks[0]);
System.out.println(Marks[1]);
System.out.println(Marks[2]);
System.out.println(Marks[3]);
System.out.println(Marks[4]);

}
}

Why we go for the looping to printing the array value because in above example array index position is only changing and also for higher value above example is too difficult

Program:

Class Arraypractice{

Public static void main(args[])
{

int[] Marks = {90, 100,79, 84, 98};

for (int i = 0; i<Marks.length; i++){

System.out.println(Marks[i]);

}
}
}

Class Arraypractice{

Public static void main(args[])
{

int[] Marks = {90, 100,79, 84, 98};

while (int i < Marks.length ){

System.out.println(Marks[i]);

}
}
}

Output:
90
100
79
84
98

3. printing the array value in reverse:

Class Arraypractice{

Public static void main(args[])
{

int[] Marks = {90, 100,79, 84, 98};

System.out.println(Marks[4]);
System.out.println(Marks[3]);
System.out.println(Marks[2]);
System.out.println(Marks[1]);
System.out.println(Marks[0]);

Output:
98
84
79
100
90

Data type in Java

SELVAKUMAR R — Thu, 30 Oct 2025 09:46:41 +0000

Attribute that tell a computer system what kind of value a variable holds and how to interpret it

In Java datatype is classified in to two types

primitive Datatype
Non primitive (Reference) Datatype

1. primitive Datatype:

1. byte

It is used to store the small whole number from -128 to 127

2. short
It is used to store the whole number from -32768 to 32767

3. int
It is used to store the whole number from - 2 billion to 2 billion

4.long
It is used to store the whole number 9 quintillion add L at end of the whole number

5. float
It store the decimal number up to 7 digit including the f at end of the decimal number

6. double
It store the decimal number up to 16 digit including the decimal

7. Boolean
It is used to provide the logical value true or false

8. char
It is used to store the single character

2. Non primitive datatype

String -> Used for storing text

Array -> Used to store multiple value in a single variable

Classes -> Used as a blueprint for creating objects

IDENTIFIER, LITERALS, KEYWORD

SELVAKUMAR R — Thu, 30 Oct 2025 05:29:26 +0000

1. Identifier:

-> Name given to various program element for identification
-> Identification name start with character (a to z or A to Z) and also start with underscore( _ ) or dollar symbol ($)

Ex:
_myvariable , $price

-> Identifer declaration cannot start with digit

Ex:
123variable , 9_price -> invalid declaration

-> Identifier are case sensitive

2. Literals:

Literals are constant values that are assigned to variable or used in expression

It cannot be changed during program execution

Types:

Integer

-> Represent whole number
-> Octal (base 8 prefixed with 0) -> Eg: 0146
-> Hexadecimal (base 16 prefixed with 0x or 0X) -> Eg: 0x65

Floating point

-> By Default the float number are in double type
-> To specify a float literal you can append f or F
Eg: float temperature : 23.5 F;

Character Literal

Represent the single character enclosed with single quotes ( ' ' )

\n -> new line
\t -> new tab
\u0041 -> unicode for 'A'

String Literal

Represent a sequence of character enclosed with double quotes ( " " )

Java treats string literal as string object

Eg:

string greeting = "Hello, Vijay" ;

Boolean Literals

It represent Logical Value -> True or False

3. Keyword

It is a reserved word cannot be used as variable , method, class name

Eg:

Data Type : int, double, boolean, float, char, byte, long, short

Control flow :if , else, for, while, do, switch, break, continue, return

class and object : class, new, extends, implements, interface, abstract, final, static, this, super

Access Modifier : public , private, protected

Exception Handling : try , catch, final, throw, throws

camel Case:

First letter of the first word is lower case

Used for variable name, method name

Eg:

int calculateTotalAmount()

Pascal Case :

First letter of every word is capitalized

Used for Class Name, Interface Name

Eg:

class MyClass

interface DataProcessor

JDK, JRE, JVM ARCHIETECTURE

SELVAKUMAR R — Tue, 28 Oct 2025 10:00:29 +0000

JDK -> Java development kit
It is complier in java complie time it covert the user code in to .class byte code
It is platform independent because it does not dependent upon the operating system to execute the program

JRE -> Java Runtime Environment

JRE holds the JVM, JIT, Java libraries for program execution
IT is platform dependent because it dependent upon the operating system to execute the code
IT make the enviornment to execute the java program

JIT-Just In Time
It act as a interpreter in JVM

JVM - Java virtual Machine

In this .class byte code is changed in to machine understandable code

History of Java

SELVAKUMAR R — Mon, 20 Oct 2025 03:12:19 +0000

Java program is released in 1995 by James Gosiling initially he named as oak due to the trade mark issue he changed the name oak to Java

Java program is platform independent because of JDK it compiles the human written code in to .class byte code file