DEV Community: Harini

String program

Harini — Wed, 22 Apr 2026 04:09:08 +0000

1. Remove extra space

name = "Kill     them      with   your    success"
result = ""
i = 0
while i < len(name):
    if name[i] != " ":
        result = result + name[i]
    else:
        if name[i-1] != " ":
            result = result + name[i]
    i += 1

print(result)

Output

2. Front space remove

name = "     kill them with your success"
i = 0
result = ""

while i < len(name):
    if name[i] != " ":
        break   
    i += 1

while i < len(name):
    result += name[i]
    i += 1

print(result)

Output

3. Remove last space

name = "Kill them with your success        "
result = ""

i = len(name)-1

while i >= 0:

    if name[i] == " ":
        i -= 1
        continue

    else:
        j = 0

        while j <= i:
            result += name[j]
            j += 1

        break

print(result)

Output

4. Reverse a word

name = input("Enter word:")
result = ""

i = len(name)-1

while i >= 0:
    result = result + name[i]
    i -= 1

print(result)

Output

String Program

Harini — Tue, 21 Apr 2026 09:07:01 +0000

1. Given string to uppercase

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. First letter to Uppercase

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. Letter Count

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

Output

4. Word count

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

Output

5. Password Validator

text=input("Enter password : ")

i=0
upper=False
lower=False
number=False
special=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=="&":
        special=True

    else:
        others=False

    i+=1

if len(text)>=8 and upper and lower and number and special and others:
    print("Valid Password")
else:
    print("Invalid Password")

Output

6. Password Generator

import random

upper="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
lower="abcdefghijklmnopqrstuvwxyz"
numbers="0123456789"
special="!@#$&"

all_chars=upper+lower+numbers+special

password=""

password=password+random.choice(upper)
password=password+random.choice(lower)
password=password+random.choice(numbers)
password=password+random.choice(special)

i=4

while i<8:
    password=password+random.choice(all_chars)
    i+=1

print("Generated Password :",password)

Output

How to Validate Indian Pincode Using Python

Harini — Mon, 20 Apr 2026 08:38:55 +0000

How to Validate Indian Pincode Using Python (Region, Sub-Region and District Finder)

regions = {
    1: "Delhi",
    2: "Uttar Pradesh & Uttarakhand",
    3: "Rajasthan & Gujarat",
    4: "Maharashtra",
    5: "Andhra Pradesh & Telangana",
    6: "Tamil Nadu & Kerala",
    7: "West Bengal & North East",
    8: "Bihar & Jharkhand",
    9: "Army Postal Service"
}

sub_regions = {
    11: "Delhi Region",
    40: "Mumbai Region",
    60: "Chennai Region",
    70: "Kolkata Region"
}

districts = {
    110: "Delhi",       111: "Delhi (North)",      112: "Delhi (South)",
    400: "Mumbai",      401: "Mumbai (Suburban)",   402: "Mumbai (West)",
    600: "Chennai",     601: "Tiruvallur",          602: "Kanchipuram",
    700: "Kolkata",     701: "Kolkata (North)",     702: "Kolkata (South)"
}

def get_pincode_details(pincode):
    if not pincode.isdigit() or len(pincode) != 6:
        print("Invalid pincode. Enter exactly 6 digits.")
        return

    num         = int(pincode)
    first_digit = num // 100000
    first_two   = num // 10000
    first_three = num // 1000

    print("Region:     ", regions.get(first_digit,   "Unknown"))
    print("Sub-region: ", sub_regions.get(first_two, "Unknown"))
    print("District:   ", districts.get(first_three, "Unknown"))


pincode = input("Enter 6-digit Pincode: ").strip()
get_pincode_details(pincode)

Output

Supermart Billing Program

Harini — Mon, 20 Apr 2026 04:04:36 +0000

Write a Java program to create a supermarket billing system using classes and objects. Calculate the final price of a product after applying discount if available. Display product details, discount percentage, and final price.

public class Supermart {

    String productName;
    int price;
    boolean discountAvailable;
    int discountPercentage;

    public Supermart(String productName, int price, boolean discountAvailable, int discountPercentage) {

        this.productName = productName;
        this.price = price;
        this.discountAvailable = discountAvailable;
        this.discountPercentage = discountPercentage;
    }

    public Supermart(String productName, int price) {

        this.productName = productName;
        this.price = price;

    }
    public static void main(String[] args) {

        Supermart p1 = new Supermart("Rice",1000,true,20);
        Supermart p2 = new Supermart("Oil",500,true,10); 
        Supermart p3 = new Supermart("Sugar",300);

        p1.display();
        p3.display();
    }

    public void display() {

        int finalPrice = price;

        if(discountAvailable) {
            finalPrice = price - (price * discountPercentage / 100);
        }

        System.out.println("Product Name: " + productName);
        System.out.println("Price: " + price);
        System.out.println("Discount Available: " + discountAvailable);

        if(discountAvailable) {
            System.out.println("Discount Percentage: " + discountPercentage);
        }

        System.out.println("Final Price: " + finalPrice);
    }

}

Output

Pincode,Gmail and Mobile Number Validation in Python

Harini — Sat, 18 Apr 2026 09:18:37 +0000

1. Check whether a given number is a valid 6-digit pincode or not.

def pincode(pc):
    if pc//100000!=0 and pc//100000<=9:
        print("Yes")
    else:
        print("No")
pincode(int(input("Enter a pincode :")))

Output

2. Check whether a given email ID is a valid Gmail address or not.

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

3. Check whether a given input is a valid Indian mobile number or not.

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

Constructor in Java

Harini — Fri, 17 Apr 2026 16:54:15 +0000

What is a Constructor?
When we make an object of a class in Java, a special method called a constructor runs automatically. The main job of this is to set the initial values for the variables inside the object.

Important Points

The name of the constructor should be the same as the name of the class.
It doesn't have a return type, not even void.
Using constructor overloading, a class can have more than one constructor.
The constructor is called automatically every time you make an object.

Syntax

class Classname{
    Classname(){
        // constructor body
    }
}

Example

public class Shop {

  public Shop() {
    System.out.println("Constructor");
  }

  public static void main(String[] args) {
    System.out.println("Main Method");

    Shop product = new Shop();
  }
}

Types of Java Constructors

Default Constructor
No-Argument Constructor
Parameterized Constructor

1. Default Constructor

Java will automatically give us a constructor if we don't make one ourselves. This is known as the default constructor. It doesn't need any parameters and sets the variables to their default values.

No arguments are needed.
Variables get default values like this:
- int = 0
- String is null and boolean is false.

Example

public class Shops {
    String name;
    int price;

    public static void main(String[] args) {
        Shops obj = new Shops();

        System.out.println(obj.name);   
        System.out.println(obj.price);  
    }
}

Output

2. No-Argument Constructor

A constructor with no parameters is called a no-argument constructor. We mostly use it when we want to give an object some set or pre-defined values when we make it.

Example

public class Shops {

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

    public static void main(String[] args) {
        Shops product = new Shops();
    }
}

Output

3. Parameterized Constructor

When we want to pass values while making an object, we use a parameterized constructor. Then, these values are used to set up the object's variables.

Example

public class Shops {
    String name;
    int price;

    public Shops(String str, int i) {
        name = str;
        price = i;
    }

    public static void main(String[] args) {

        Shops product1 = new Shops("Bag", 100);
        Shops product2 = new Shops("Note", 40);

        product1.display();
        product2.display();
    }

    public void display() {
        System.out.println(name + " " + price);
    }
}

Output

Test Case

Harini — Wed, 15 Apr 2026 16:08:23 +0000

What is a Test Case?

A test case is a set of conditions, inputs, and actions used to validate whether a specific feature of an application works correctly.

It defines what to test, how to test, and expected results
It acts as a blueprint for testing
It helps ensure the system works in normal, error, and edge conditions

Components of a Test Case

A standard test case includes:

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

What is a Test Scenario?
A test scenario is a high-level idea of what you want to test in a product or application.

Test Case vs Test Scenario

Test Scenario → What to test (high-level)
Test Case → How to test (detailed steps)

How to Write Test Cases

Understand requirements
Identify test scenarios
Write clear test case name
Define preconditions
Write step-by-step actions
Add test data
Define expected result
Execute and record actual result

Example: Invalid Password

Test Case Table

Top SDLC Models Every Developer Should Know

Harini — Mon, 13 Apr 2026 04:32:44 +0000

What is SDLC?

SDLC (Software Development Life Cycle) is a step-by-step process used to develop high-quality software.

Phases of SDLC:

Requirement Gathering
Planning
Designing
Development
Testing
Implementation and Maintenance

What are SDLC Models?

SDLC Models are different approaches used to execute the SDLC phases.

Each model is chosen based on:

Project size
Requirements clarity
Risk level
Timeline

Types of SDLC Models
1. Waterfall Model
Definition:

A linear and sequential model where each phase is completed before moving to the next.

Advantages:

Simple and easy to understand
Well-structured
Good for small projects

Disadvantages:

No flexibility
Difficult to handle changes

2. Agile Model
Definition:

An iterative and flexible model where development is done in small parts called sprints.

Advantages:

Handles changing requirements
Continuous feedback
Faster delivery

Disadvantages:

Requires experienced team
Less documentation

3. V-Model (Validation & Verification)
Definition:

Each development phase has a corresponding testing phase.

Advantages:

Early testing
High quality

Disadvantages:

Rigid structure
Not flexible

Choosing the right SDLC model is important for project success.

Use Waterfall when requirements are fixed
Use Agile when requirements change frequently
Use V-Model when testing is critical

Encryption and Decryption

Harini — Sat, 11 Apr 2026 17:13:09 +0000

In today’s digital world, protecting information is very important. Whether it’s personal data, banking details, or online communication, encryption and decryption ensure that sensitive information stays secure.

What is Encryption?

Encryption is the process of converting a normal, readable message (plaintext) into an unreadable format called ciphertext.

This ciphertext looks meaningless and cannot be understood without a proper decryption key.

Example:

Plaintext:
HELLO

Ciphertext:
KHOOR

Here, each letter is shifted by 3 positions (Caesar Cipher).

Caesar Cipher
The Caesar cipher is a very simple and old method of hiding messages. It works by changing each letter in a message to another letter by moving a fixed number of steps in the alphabet.

For example, if we use a shift of 3:

A becomes D
B becomes E

So, every letter is just moved 3 positions forward (or backward) to create a secret message.

Types of Encryption
1. Symmetric Encryption

Uses the same key for encryption and decryption
Faster and efficient

2. Asymmetric Encryption
Uses two keys:

Public Key (for encryption)
Private Key (for decryption) More secure but slower

What is Decryption?

Decryption is the reverse process of encryption. It converts the unreadable ciphertext back into its original readable form (plaintext).

It is the reverse of encryption.

Example:

Cipher text:
KHOOR

Decrypted:
HELLO

How Encryption and Decryption Work

A sender writes a message (plaintext)
Encryption algorithm + key converts it into ciphertext
The encrypted data is transmitted
The receiver uses a key to decrypt it
The original message is restored

Why Encryption and Decryption are Important

Maintain privacy
Protect sensitive data
Secure communication over the internet
Prevent cyber attacks and data theft

They ensure confidentiality, integrity, and security of information.

Self Introduction

Harini — Thu, 09 Apr 2026 16:23:25 +0000

My name is Harini.And I'm from Chennai.I completed my Bachelor's degree in Computer Science and Engineering from Mookambigai College of Engineering,Pudukkottai.

Coming to my technical skills,I have got a good foundation in HTML,CSS and JavaScript.

I have done small projects like a youtube clone and a google login page using HTML,CSS and JavaScript,which helped me to improve my frontend development skills.

For my academic projects,I worked on "Secure medical data collaboration using Federated learning".In this project,we focused on protecting sensitive medical data while allowing multiple parties to collaborate securely.This helped me to understand both technical concepts and the importance of data security.

I am a quick learner,passionate about web development,and always interested in learning new technologies.I am looking for oppurtunities where I can improve my skills and contribute to real-world projects.

Understanding Constructor Functions in JavaScript

Harini — Thu, 09 Apr 2026 07:28:38 +0000

In JavaScript, a constructor function is used to create multiple objects with similar properties and methods. Instead of creating objects manually again and again, we use a constructor to generate them easily.

What is an Object?

An object stores data in key–value pairs.

Example:

let person = {
  name: "Harini",
  age: 22
};

Here:

name and age are keys
"Harini" and 23 are values If we want to create many similar objects, writing this structure repeatedly is not efficient. That’s why we use constructor functions.

What is a Constructor Function?

A constructor function is a normal function used to create objects.

By convention, constructor function names should start with a capital letter.
Example:

function User() {
  this.name = "Harini";
}

Here:

this refers to the newly created object.
this.name assigns a property to that object.

Creating an Object Using new
To create an object from a constructor, we use the new keyword.

let user1 = new User();
console.log(user1);

What happens when we use new?

When we write new User():

A new empty object is created.
this refers to that new object.
Properties are added to the object.
The object is returned automatically.

We do not need to manually write return this.

Creating Multiple Objects

Each time we use new, a new object is created.

let user1 = new User();
let user2 = new User();

Both user1 and user2 are separate objects.

Constructor with Arguments

Constructor functions can also accept parameters.

Example:

function User(name) {
  this.name = name;
}

let user1 = new User("Harini");
console.log(user1);

Now the value is passed dynamically instead of being hardcoded.
This makes the constructor more flexible.

Adding Properties and Methods
We can add both properties and methods inside a constructor.
Example:

function User(name, age) {
  this.name = name;
  this.age = age;
  this.getAge = function() {
    return this.age;
  };
}

let user1 = new User("Harini", 22);
console.log(user1.getAge());

Here:

name and age are properties.
getAge() is a method.
Methods are called using parentheses.

Important Points to Remember

Constructor function names should start with a capital letter.
Always use the new keyword to create objects.
this refers to the newly created object.
Each new call creates a separate object.

Learn ASCII with Easy Examples in Python and JavaScript

Harini — Wed, 08 Apr 2026 14:15:21 +0000

What is ASCII?

ASCII (American Standard Code for Information Interchange) is a character encoding system used to represent text in computers using numbers.

Each character—such as letters (A–Z, a–z), digits (0–9), and symbols (@, #, etc.)—is assigned a unique numeric value called an ASCII value.

Example

'A' → 65
'a' → 97
'1' → 49
'@' → 64

Why ASCII is Important

Helps computers store and process text
Used in programming and string manipulation
Foundation for modern encoding systems like Unicode

JavaScript

let name = "silambu9391a@gmail.com";

for (let i = 0; i < name.length; i++) {
    console.log(name[i] + " : " + name.charCodeAt(i));
}

How it works

name[i] -> gets the character
name.charCodeAt(i) -> gets ASCII value of that character

Python

name = "silambu9391a@gmail.com"

for ch in name:
    print(ch, ":", ord(ch))

How it works

for ch in name → loops through each character
ord(ch) → gives ASCII value of that character

Output