DEV Community: Divya Divya

What is POJO in Java?

Divya Divya — Tue, 12 May 2026 04:59:18 +0000

POJO(Plain Old Java Object:

A Java Programming POJO (Plain Old Java Object) is a simple normal Java class that is not connected to any special framework or restriction.Is not dependent on frameworks like EJB.
It does not need special classes, interfaces, or dependencies.
A POJO usually contains fields, constructors, getters, setters, and normal methods.

Why is POJO?

POJO is used to create simple Java classes.
It makes code easy to write and understand.
It helps to store object data like name, age, id, etc.
It improves code reusability.
It is easy to test and maintain.

Example:

class Student {
    private String name;
    private int age;

    // Constructor
    Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Getter
    public String getName() {
        return name;
    }

    // Setter
    public void setName(String name) {
        this.name = name;
    }

    public static void main(String[] args) {

        Student s1 = new Student("Divya", 20);

        System.out.println(s1.getName());
    }
}

Output

Method Overriding in Java

Divya Divya — Tue, 05 May 2026 18:49:44 +0000

When a subclass provides a specific implementation for a method that is already defined in its parent class, it is called method overriding. The overridden method in the subclass must have the same name, parameters, and return type as the method in the parent class.

Rules for Method Overriding

Name, parameters, and return type must match the parent method.
Java picks which method to run at run time, based on the actual object type, not just the reference variable type.
Static methods cannot be overridden.

Usage of Java Method Overriding

Method overriding is used for achieving run-time polymorphism.
Method overriding is used for writing specific definition of a subclass method (this method is known as the overridden method).

class Animal {

    void move(){
        System.out.println(
      "Animal is moving."); 

    }
    void eat(){

        System.out.println(
      "Animal is eating."); 

    }
}

class Dog extends Animal{

    @Override void move(){ 

      // move method from Base class is overriden in this
      // method
        System.out.println("Dog is running.");
    }
    void bark(){

        System.out.println("Dog is barking."); 

    }
}

public class Geeks {
    public static void main(String[] args)
    {
        Dog d = new Dog();
        d.move(); 
        d.eat(); 
        d.bark();
    }
}

To be discused
Output

Access Modifiers in Java

Divya Divya — Mon, 04 May 2026 18:15:00 +0000

Every Java developer writes classes, methods, and fields. But who should be allowed to use them? Access modifiers answer exactly that — they control visibility, enforce encapsulation, and form the foundation of clean API design.

Java has four:

Default (Package-private)
Private
Protected
Public

Let's break each one down.

Default Access Modifier

If no access modifier is specified, the member has default (package-private) access and can only be accessed within the same package.This means only classes within the same package can access it.
Example

class Car {
    String model; // default access
}

public class Main {

    public static void main(String[] args){

        Car c = new Car();
        c.model = "Tesla"; // accessible within the same package
        System.out.println(c.model);
    }
}

Output

Private Access Modifier

The private access modifier is specified using the keyword private. The methods or data members declared as private are accessible only within the class in which they are declared.

Example

class Person {

    // private variable
    private String name;

    public void setName(String name)  {

        this.name = name; // accessible within class
    }

    public String getName() { return name; }
}

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

        Person p = new Person();
        p.setName("Alice");

        // System.out.println(p.name); // Error: 'name'
        // has private access
        System.out.println(p.getName());
    }
}

Output

Protected Access Modifier

The protected access modifier is specified using the keyword protected. The methods or data members declared as protected are accessible within the same package or subclasses in different packages.

Example

// File: Vehicle.java in package p1
package p1;
public class Vehicle {
    protected int speed;
}

// File: Bike.java in package p2
package p2;
import p1.Vehicle;
public class Bike extends Vehicle {
    void showSpeed() {
        speed = 100; // allowed: subclass in different package
        System.out.println(speed);
    }
}

// File: Test.java in package p2
package p2;
import p1.Vehicle;
public class Test {
    public static void main(String[] args) {
        Bike b = new Bike();
        b.showSpeed(); // prints 100

        Vehicle v = new Vehicle();
        // System.out.println(v.speed); // ERROR: cannot access protected outside package & non-subclass
    }
}

Output

Public Access Modifier

The public access modifier is specified using the keyword public. Public members are accessible from everywhere in the program. There is no restriction on the scope of public data members.

Example

class MathUtils { 

    public static int add(int a, int b) {
        return a + b;
    }
}

public class Main {

    public static void main(String[] args) {

        System.out.println(MathUtils.add(5, 10)); // accessible anywhere
    }
}

Output

Private:
The idea should be use as restrictive access as possible, so private should be used as much as possible.
Default (Package-Private):
Often used in package-scoped utilities or helper classes.
Protected:
Commonly used in inheritance-based designs like framework extensions.
Public:
This is used for API endpoints, service classes, or utility methods shared across different parts of an application.

What is package in java

Divya Divya — Mon, 04 May 2026 17:35:51 +0000

Java Package is used to group related classes .

avoiding name conflicts: (two classes with the same name can exist in different packages).
Reusability: packaged code can be imported and used anywhere. Packages are divided into two categories;

Build in packages(Packages from the java API
User-defined Packages (create your own packages)

Build in Package:
Built-in Packages comprise a large number of classes that are part of the Java API. Some of the commonly used built-in packages are:

java.lang: Contains language support classes
java.io: Contains classes for supporting input/output operations.
java.util: Contains utility classes that implement data structures such as Linked Lists and Dictionaries, as well as support for date and time operations.
java.applet: Contains classes for creating Applets.
java.awt: Contains classes for implementing the components for graphical user interfaces (like buttons, menus, etc). 6)

Example: Using java.util.Random (Built-in Package)

import java.util.Random;   // built-in package

public class GFG{

    public static void main(String[] args) {

        // using Random class
        Random rand = new Random();   

        // generates a number between 0–99
        int number = rand.nextInt(100);  

        System.out.println("Random number: " + number);
    }
}

Output

User-defined Packages

User-defined Packages are the packages that are defined by the user.

Example:

package com.myapp;

public class Helper {
    public static void show() {
        System.out.println("Hello from Helper!");
    }
}

To use it in another class:

import com.myapp.Helper;

public class Test {
    public static void main(String[] args) {
        Helper.show();
    }
}

String Program ?

Divya Divya — Sat, 02 May 2026 03:23:35 +0000

1. Full String Upper

text=input("Enter some words: ")
i=0
upper=""
while i<len(text):
    ch=text[i]
    if ch>="a" and ch<="z":
        upper=upper+chr(ord(ch)-32)
    else:
        upper=upper+ch
    i+=1
print(upper)

Output:

2. Every First Letter Upper


text=input("Enter some words: ")
i=0
upper=""
while i<len(text):
    ch=text[i]
    if (ch>="a" and ch<="z")and(text[i-1]=="" or i==0):
        upper=upper+chr(ord(ch)-32)
    else:
        upper=upper+ch
    i+=1
print(upper)

Output

3. First Letter only Uppercase

text=input("Enter some words: ")
i=0
count=0
upper=""
while i<len(text):
    ch=text[i]
    if (ch>="a" and ch<="z")or(ch>="A" and ch<="Z"):
        count+=1
    else:
        upper=upper+ch
    i+=1
print(count)

Output:

4. Word Counter

text=input("Enter some words: ")
i=0
count=1
upper=""
while i<len(text):
    ch=text[i]
    if text[i]!=" " and text[i-1]==" ":
        count+=1
    i+=1
print(count)

Output

5. Password Verify

text=input("Create your password :")
i=0
upper=False
lower=False
number=False
spacial=False
others=True
while i<len(text):
    ch=text[i]
    if ch>="A" and ch<="Z":
        upper=True
    elif ch>="a" and ch<="z":
        lower=True
    elif ch>="0" and ch<="9":
        number=True
    elif ch=="!" or ch=="@" or ch=="#" or ch=="$" or ch=="&":
        spacial=True
    else:
        others=False
    i+=1
if upper and lower and number and spacial and others:
    print("password succesfully create")
elif not upper:
    print("please inclued upper char in password")
elif not lower:
    print("please inclued lower char in password")
elif not number:
    print("please inclued number in password")
elif not spacial:
    print("please inclued spacial chars: ! @ # $ & in password")
else:
    print("spacial  charactor only allow !, @, #, $, & ")

Output

Java Constructor Program

Divya Divya — Sun, 19 Apr 2026 18:49:20 +0000

Product Program

class Dmart{ 

String productname;
int proprice;
boolean prodiscount;
int prodiscountpercentage;
int discountprice;
int finalprice;


public Dmart(String name ,int price ,boolean discount,int discountpercentage){

this.productname=name;
this.proprice=price;
this.prodiscount=discount;
this.prodiscountpercentage=discountpercentage;
}


public static void main(String[] args){

Dmart product1=new Dmart("Mobile" , 70000 ,true , 8);
Dmart product2=new Dmart("Watch" , 300 , true , 5);
Dmart product3=new Dmart("Choclate" , 450 , true , 2);
Dmart product4=new Dmart("Biscut"  ,  30 , true , 7);
Dmart product5=new Dmart("HotChips" , 25 , true ,12);

product1.buy();
product2.buy();
product3.buy();
product4.buy();
product5.buy();

}
public void buy(){

this.discountprice = (this.proprice * this.prodiscountpercentage) / 100;
this.finalprice=this.proprice-this.discountprice;

System.out.println("productname => "+ this.productname);
System.out.println("proprice => " + this.proprice);
System.out.println("prodiscount => "  + this. prodiscount);
System.out.println("prodiscountpercentage => " + this.prodiscountpercentage);
System.out.println("discountprice => " + this.discountprice);
System.out.println("finalprice => " + this.finalprice);

}

}

Output:

Mobile Number , G-mail , Pin Code Validation

Divya Divya — Sat, 18 Apr 2026 03:35:09 +0000

Mobile Number Validation

def verify(mobnum):
    index=0
    while index<len(mobnum):
        if mobnum[index]>="0" and mobnum[index]<="9":
            index+=1
            continue;
        else:
            return False
    return True



def mobile(n):
    i=0
    while i<len(n):
        if(n[i]>="0" and n[i]<="9") or (n[i]=="+") or (n[i]==" "):
            i+=1
        else:
            return "characters and special charactors not allowed"

    if len(n)==10:
        if n[0]>="6" and n[0]<="9" and verify(n):
            return "valid";
        else:
            return "incorrect"

    if len(n)==13:
        if n[0:3]=="+91":
            if n[3]>="6" and n[3]<="9" and verify(n[3:]):
                return "valid"
            else:
                return "incorrect"
        return "First three number should like +91"

    if len(n)==14:
        if n[0:4]=="+91 ":
            if n[4]>="6" and n[4]<="9" and verify(n[4:]):
                return "valid"
            else:
                return "incorrect"
        return "First four number should like +91 "
    return "Please Enter Your valid Mobile Number"      
print(mobile(input("Enter Your Mobile  Number : ")));

Output:

Gmail Validation

def verify_Gmail(Gmail):
    if Gmail[-10:]=="@gmail.com":
        i=0
        gmailcopy=Gmail[0:len(Gmail)-10]
        while i<len(gmailcopy):
            current=gmailcopy[i]
            i+=1
            if current>="a" and current<="z":
                continue;
            elif current>="A" and current<="Z":
                continue;
            elif current>="0" and current<="9":
                continue;
            elif current=="." or current=="_":
                continue;
            else:
                return False
        return True
    else:
        return False

if verify_Gmail(input("Enter Your Gmail :")):
    print("valid")
else:
    print("invalid")

Output:

Pin code Validation

const tamilNaduPincode = {
            region: {
                6: "Tamil Nadu & Kerala"
            },

            subRegion: {
                60: "Chennai Region",
                61: "Northern Tamil Nadu Region",
                62: "Southern Tamil Nadu Region",
                63: "Central Tamil Nadu Region",
                64: "Western Tamil Nadu Region"
            },

            district: {
                600: "Chennai",
                601: "Tiruvallur",
                602: "Kanchipuram",
                603: "Chengalpattu",
                604: "Villupuram",
                605: "Cuddalore",
                606: "Tiruvannamalai",
                607: "Cuddalore (Rural)",
                608: "Nagapattinam",
                609: "Mayiladuthurai",

                610: "Tiruvarur",
                611: "Nagapattinam",
                612: "Thanjavur",
                613: "Thanjavur",
                614: "Thiruvarur",
                615: "Ariyalur",
                616: "Perambalur",
                617: "Karur",
                618: "Karur",
                619: "Nagapattinam",

                620: "Tiruchirappalli",
                621: "Perambalur",
                622: "Pudukkottai",
                623: "Ramanathapuram",
                624: "Dindigul",
                625: "Madurai",
                626: "Virudhunagar",
                627: "Tirunelveli",
                628: "Thoothukudi",
                629: "Kanyakumari",

                630: "Sivagangai",
                631: "Kanchipuram",
                632: "Vellore",
                633: "Vellore",
                634: "Krishnagiri",
                635: "Dharmapuri",
                636: "Salem",
                637: "Namakkal",
                638: "Erode",
                639: "Karur",

                640: "Coimbatore",
                641: "Coimbatore",
                642: "Coimbatore (Pollachi)",
                643: "Nilgiris"
            }
        };
        function getPincodeDetails(pincode) {
            let firstDigit = Math.floor(pincode / 100000);
            let firstTwo = Math.floor(pincode / 10000);
            let firstThree = Math.floor(pincode / 1000);

            console.log("Region: ", tamilNaduPincode.region[firstDigit]);
            console.log("Sub-region: ", tamilNaduPincode.subRegion[firstTwo]);
            console.log("District:", tamilNaduPincode.district[firstThree]);
        }

        getPincodeDetails(606902);

Output:

To be discussed...

Constructor in Java

Divya Divya — Sat, 18 Apr 2026 03:03:13 +0000

What is Constructor:

Constructor is a Special method in Java.
When object is create , it's automatically called.
Constructor it helps to object set the initial value.
Giving an initial value to a variable when it is created.

Default Constructor:

Default Constructor is no arguments in the constructor.
You don't define the constructor , Java is given the default constructor.
If you do NOT write any constructor → the compiler will automatically create a default (no-argument) constructor.
Purpose of constructor provides default values (0,null).

Example:

 class Person{
     String name;
     int age;

public static void main(String[] args){
    Person s1=new Person();

System.out.println(s1.name);
System.out.println(s1.age);
}
 }

Output:

Parameterized Constructor

A parameterized constructor is a special method in Java.
It is used to set values when an object is created.
Unlike a default constructor (which gives common values like 0 or null).
a parameterized constructor lets you pass your own values.
You can give values while creating the object.
It sets those values to the object’s variables (fields)

Output

 class Person{
     String name;
     int age;



public Person(String a , int b){
    name=a;
    age=b;
}

public static void main(String[] args){
    Person s1=new Person("Divya" , 21);

System.out.println(s1.name);
System.out.println(s1.age);
}
 }

Output

No-Arguments Constructor

This Constructor created by programmer
It has a no parameters
It helps to some specific code run , at the time of object creation
It is used to set a common values and message print.
Purpose of Zero argument constructor , assigns custom starting values.

Example

public class Person {

    public Person() {
        System.out.println("No-argument");
    }

    public static void main(String[] args) {
        Person s1 = new Person();
    }
}

Output

Test Case

Divya Divya — Thu, 16 Apr 2026 03:32:12 +0000

What is TestCase?

A Test Case is a step-by-step guide used to check if a specific part of a software application works correctly as expected.
It defines the actions to be taken, the required data, and the expected result to validate that a feature functions as per the requirements.

Why TestCase is Important?
Test cases are crucial for ensuring software quality by defining specific steps, inputs, and expected outcomes to validate functionality, verify requirements, and catch bugs early.

Reason:

Validate Requirements and Functionality.
Early Defect Identification.
Consistency and Repeatability.
Regression Testing & Risk Management.
Documentation and Knowledge Transfer.
Foundation for Automation.

Components of a Test Case:

A standard test case includes:

Test Case ID
Test Scenario / Name
Test Case
Preconditions
Test Steps
Expected Result
Status (Pass/Fail)

TestCase Format:

What is URL?

Divya Divya — Sun, 12 Apr 2026 02:54:39 +0000

URL(Uniform Resource Location):

URL is full address used to find something on the internet, like a webpage or file.
It tells your browser where to go and how to get the data.

Part of URL:

Protocol: (http , https) => How to access the resource. It tells how to fetch data.

Data Fetch means:Getting data from a server or API and using it.

Explain:
When you open a website (like Instagram or YouTube), the data shown on your screen (posts, videos, users) is not stored locally. It is stored on a server. We fetch that data from the server and bring it to the browser. This process is called fetching.

Domain: tells which website.

Explain:
A computer actually has an IP address (like 142.250.190.78), but it is difficult to remember. So, for easy to use, we use a domain name instead of the IP address.”

Example: YouTube.com ,Google.com , amazon.in.

Path: Tells which page.

Explain:

https://example.com/about
example.com → website
/about → path
Go to the About page.

Why good URLs important:

Easy to understand
Easy to Share
Helps search engines understand your site.

SEO (Search Engine Optimization)means: Make your website for search engine to find , understand , and recomend to user

So, a clean and clear URL makes ypur website better.

URL Structure

A URL (Uniform Resource Locator) consists of several parts that pinpoint a specific web resource's location.

https:// Scheme:
Defines the protocol used to access the resource.

www. Subdomain:
Specifies a subdivision of the main domain .

example. Domain:
Identifies the main website name.

com Top-Level Domain:
Indicates the domain extension.

:443 Port Number:
Specifies the server port.

/blog/article/search Path:
Points to the resource location on the server.

? Query:
The ? symbol that starts query parameters.

docid=720&hl=enParameters:
Passes data as key-value pairs using &.

#dayone Fragment:
Refers to a specific section within the resource using #.

Self-Introduction

Divya Divya — Thu, 09 Apr 2026 18:18:41 +0000

I'm Divya. I am from Velachery.

I have completed my Bachelor of Computer Applications (BCA) from Sri Saradha College for Women’s, Perambalur.

I am passionate about learning new technologies and continuously improving my skills. I have knowledge of HTML, CSS, and JavaScript, and I can build interactive and user-friendly websites.

I have worked on small projects such as a YouTube clone, a Google homepage clone, and a login page using HTML, CSS, and JavaScript. These projects helped me strengthen my front-end development skills.

I am looking for an opportunity where I can start my career, enhance my skills, and contribute to the organization.

Thank you for this opportunity.

Self-Introduction

Divya Divya — Thu, 09 Apr 2026 18:06:42 +0000

I'm Divya , I'm From Velachery,I have completed my degree BCA (Computer Applications) at Sri Saradha College for Women's in Perambalur.

I'm Passionate about learning new technologies and improving my skills.I have knowledge of HTML , CSS and JavaScript , and I can build interactive websites.

I have done small projcets like a Youtube clone , Google homepage clone and a login page using HTML , CSS and JavaScript.

I'm looking for this opportunity will help me build my career and enhance my skills. Thank you for giving me this opportunity.