DEV Community: Vidya

Remove Space Programs

Vidya — Wed, 22 Apr 2026 04:19:17 +0000

1.Remove Front Space:

name="practice makes    perfect"
i=0
result=""
while i<len(name):
  if name[i]!=" ":
    result=result+name[i]
  else:
    if i>0 and name[i-1]!=" ":
      result=result+name[i]
  i+=1
print(result)

Output:

2.Remove Extra Space:

name="practice makes    perfect"
i=0
result=""
while i<len(name):
  if name[i]!=" ":
    result=result+name[i]
  else:
    if i>0 and name[i-1]!=" ":
      result=result+name[i]
  i+=1
print(result)

output:

3.Remove Back 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 The Word:

name = "PULIKESI"
result = ""

i = len(name)-1

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

print(result)

output:

5. 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:

String Programs

Vidya — Tue, 21 Apr 2026 08:45:31 +0000

1.Lowercase 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 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.Counting Letters

 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.Counting Words

 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("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 validate")
else:
    print("invalied try another")

output:

Comparable Interface in Java

Vidya — Tue, 21 Apr 2026 04:51:55 +0000

Comparable Interface

The Comparable Interface in Java is used to define the natural ordering of objects within a class. It is available in the java.lang package and contains only one method called compareTo(). By implementing this interface, a class can specify how its objects should be compared and sorted. It is commonly used with sorting methods like Collections.sort() or Arrays.sort().

Example:

 import java.util.*;

class Student implements Comparable<Student> {
    int age;
    String name;

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

    public int compareTo(Student s) {
        return this.age - s.age; // sorting by age
    }
}

public class Main {
    public static void main(String[] args) {
        ArrayList<Student> list = new ArrayList<>();
        list.add(new Student(22, "A"));
        list.add(new Student(18, "B"));
        list.add(new Student(20, "C"));

        Collections.sort(list);

        for (Student s : list) {
            System.out.println(s.age + " " + s.name);
        }
    }
}            --> output: 18 B  
                         20 C  
                         22 A

Real-Time theoretical examples of the Comparable Interface

1. Bank Transactions Sorting

In banking apps, transactions are sorted by date or amount. Using Comparable, transactions can have a natural order like latest first.

2. Flight Ticket Booking Systems

Airlines sort flights by departure time or ticket price so users can easily choose the best option.

3. Hospital Patient Priority

Hospitals may sort patients based on severity level or emergency priority to decide treatment order.

Why we use Comparable?

We use the Comparable Interface in Java to define a natural sorting order for objects of a class. It allows objects to be compared with each other using the compareTo() method, so they can be easily sorted. This is useful when working with collections like lists, where we want automatic ordering without writing extra logic every time. Overall, it helps make sorting simple, consistent, and built directly into the class itself.

Pincode Details Finder

Vidya — Mon, 20 Apr 2026 06:06:58 +0000

Pincode Details Finder (Python Program)
This program takes a 6-digit pincode as input and validates whether it is correct or not. It extracts the first digit, first two digits, and first three digits to identify the region, sub-region, and district. Using predefined lists, it matches these digits to their respective names. Finally, it displays the location details if valid, otherwise shows an error message.

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 Pincode: ").strip()
get_pincode_details(pincode)

output:

ArrayList Methods

Vidya — Sun, 19 Apr 2026 14:43:17 +0000

1.Adding Elements

ArrayList<String> list = new ArrayList<>();
list.add("Apple");
System.out.println(list); --> output:[Apple]

2.Accessing Elements

ArrayList<String> list = new ArrayList<>();
list.add("Apple");

String item = list.get(0);
System.out.println(item); -->output:Apple

3. Updating Elements

import java.util.ArrayList;

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

        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");

        list.set(0, "Mango");   // replace element

        System.out.println(list);
    }
}  

output:[Mango, Banana]

4. Removing Elements

import java.util.ArrayList;

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

        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Mango");

        list.remove(0);          // remove by index
        System.out.println(list);

        list.remove("Banana");   // remove by value
        System.out.println(list);

        list.clear();            // remove all
        System.out.println(list);
    }
}

  output:[Banana, Mango]
         [Mango]
         []

5. Size & Check

import java.util.ArrayList;

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

        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");

        System.out.println(list.size());           // number of elements
        System.out.println(list.isEmpty());        // check empty
        System.out.println(list.contains("Apple"));// check element
    }
}

output:2
       false
       true

6. Searching

 import java.util.ArrayList;

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

        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Apple");

        System.out.println(list.indexOf("Apple"));      // first index
        System.out.println(list.lastIndexOf("Apple"));  // last index
    }
}

output:0
       2

7. Bulk Operations

import java.util.ArrayList;

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

        ArrayList<String> list = new ArrayList<>();
        list.add("Apple");
        list.add("Banana");
        list.add("Apple");

        System.out.println(list.indexOf("Apple"));      // first index
        System.out.println(list.lastIndexOf("Apple"));  // last index
    }
}

output:[Apple, Banana, Grapes]
       [Apple, Banana]
       [Grapes]

Programs for Pincode, Gmail, and Mobile Number Validation

Vidya — Fri, 17 Apr 2026 16:58:51 +0000

1.Write a program to check whether a given Gmail ID is valid or not.

Python

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

2. Write a program to check whether a given pincode is valid or not. A valid pincode must contain exactly 6 digits.

Python

         pincode = int(input("Enter a pincode: "))

                count = 0
                temp = pincode

                while temp > 0:
                    temp = temp // 10
                    count += 1

                if count == 6 and pincode >= 100000 and pincode <= 999999:
                    print("YES")
                else:
                    print("NO")

output

3.Write a program to check whether a given mobile number is valid or not.

Python

 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":
            return "valid";
        else:
            return "First number should not be less then 6 "
    if len(n)==13:
        if n[0:3]=="+91":
            if n[3]>="6" and n[3]<="9":
                return "valid"
            else:
                return "Fourth number should not be less then 6"
        else:
            return "First three number should like +91"
    if len(n)==14:
        if n[0:4]=="+91 ":
            if n[4]>="6" and n[4]<="9":
                return "valid"
            else:
                return "fifth number should not be less then 6"
        return "First four number should like +91 "
    return "Please Enter Your valid Mobile Number"      
print(mobile(input("Enter Your Mobile  Number : ")));

output

Java Collections, ArrayList, Wrapper Class & Memory Management (Stack vs Heap)

Vidya — Fri, 17 Apr 2026 16:28:45 +0000

Java Collections Hierarchy (Image Format)

              Collection (Interface)
                        |
        ---------------------------------
        |                               |
     List (Interface)               Set (Interface)
        |                               |
   ------------------          ---------------------
   |        |       |          |        |         |
ArrayList LinkedList Vector   HashSet LinkedHashSet TreeSet
  (Class)    (Class) (Class)   (Class)   (Class)    (Class)

What is ArrayList?
ArrayList is a class in Java that implements the List interface and is part of the Collection framework. It uses a dynamic array, meaning its size can grow or shrink automatically when elements are added or removed. ArrayList maintains the insertion order and allows duplicate elements. It is widely used because it provides fast access to elements using index positions.
Examples

import java.util.*;

class Demo {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(10);
        list.add(20);
        list.add(10);

        System.out.println(list);
    }
}

Output:

[10, 20, 10]

What is Wrapper Class?
A wrapper class converts primitive data types → objects.

Examples:


       Primitive        Wrapper Class
       int              Integer
       char             Character
       double               Double
       boolean              Boolean

Example:
int a = 10;
Integer obj = a; // Autoboxing

What happens when we print Wrapper Class?
Integer obj = 100;
System.out.println(obj);
Output:
--> 100
Internally:
--> Wrapper class overrides toString()
--> So it prints value, not memory address

Stack vs Heap


┌─────────────────────┬────────────────────────┬────────────────────────┐
│  Type                 Stored in Stack          Stored in Heap      │
├─────────────────────┼────────────────────────┼────────────────────────┤
│   Primitive (int)      Yes                       No                 │
├─────────────────────┼────────────────────────┼────────────────────────┤
│   Wrapper Object       Reference only           Object             │
├─────────────────────┼────────────────────────┼────────────────────────┤
│   ArrayList           Reference only            Object             │
└─────────────────────┴────────────────────────┴────────────────────────┘

Collection in Java

Vidya — Thu, 16 Apr 2026 15:23:55 +0000

What is Collection in Java?
In Java, a Collection is a framework that provides a set of classes and interfaces to store and manage groups of objects (data).It belongs to the package Java Collections Framework.

Why we use Collection in Java?
We use collections because:
1. Dynamic size – Unlike arrays, collections can grow or shrink automatically.
2. Easy data handling – Sorting, searching, inserting, deleting becomes simple.
3. Reusable code – Built-in methods reduce coding effort.
Better performance – Optimized data structures.
4. Multiple data structures – List, Set, Queue, Map for different needs.

Why we use Interface in Collection?
Interfaces are used because:
1.Abstraction
Interface defines what operations to perform (like add, remove), but not how they are implemented.
2.Flexibility
You can easily switch implementations without changing code logic.
Example:

List<String> list = new ArrayList<>();

Here:

List = Interface
ArrayList = Class

✔ Tomorrow you can change to:

List<String> list = new LinkedList<>();

(No need to change logic)

Why we use Classes in Collection?
Classes provide the actual implementation of interfaces.

Example:

ArrayList → dynamic array
LinkedList → doubly linked list

✔ They contain logic to store and manage data.

Why we use Methods in Collection?
Methods help to perform operations on data easily.

Common methods:

add() → insert element
remove() → delete element
size() → count elements
contains() → check element

Example:

list.add("Java");
list.remove("Java");
System.out.println(list.size());

Test Cases

Vidya — Wed, 15 Apr 2026 15:54:57 +0000

What is a Test Case?
A test case is a set of conditions or steps used to check whether a software application is working correctly or not.

Why do we use Test Cases?
We use test cases to ensure the software works properly and meets requirements.

Main reasons:

1.To verify functionality
→ Check if each feature works as expected
2.To find bugs
→ Helps identify errors in the application
3.For reusability
→ Same test case can be used again in regression testing
4.For documentation
→ Keeps a record of testing process
5.To improve quality
→ Ensures better and reliable software

Test Case Table - Registration Form

SDLC

Vidya — Mon, 13 Apr 2026 04:38:34 +0000

What is SDLC?
SDLC (Software Development Life Cycle) is a step-by-step process used to develop software in a structured and efficient way.

It ensures:
High-quality software
Proper planning and execution
Reduced cost and time

SDLC Phases (Simple Understanding)
1.Requirement Gathering – Understand what the user needs
2.Design – Plan how the software will work
3.Development (Coding) – Write the code
4.Testing – Check for errors
5.Deployment – Release the software
6.Maintenance – Fix issues and update features

SDLC Models with Examples
1. Waterfall Model
Linear process (step by step, no going back)
Example:
Developing a college management system
First finalize requirements (students, marks, fees)
Then design → code → test → deploy
No changes allowed after moving forward
2. V-Model
Development + Testing side by side
Example:
Building banking software
While designing login system → also plan login testing
Each stage has a testing phase
3. Incremental Model
Build software in parts
Example:
Creating an e-commerce app
First release: Login + Product view
Second release: Add to cart
Third release: Payment system
4. Iterative Model
--> Repeated improvements
Example:
Developing a mobile app
Version 1: Basic features
Version 2: UI improvement
Version 3: Add new features based on feedback
5. Spiral Model
--> Focus on risk analysis + iteration
Example:
Developing air traffic control software
Plan → Identify risks → Develop → Test → Repeat
Each loop reduces risk
6. Agile Model
--> Flexible and fast development
Example:
Building a food delivery app
Develop small features (like login, order, tracking) in short cycles (sprints)
Continuous feedback from users
7. DevOps Model
--> Development + Operations together
Example:
Apps like online streaming platforms
Continuous updates and deployment
Automatic testing and delivery
8. Big Bang Model
--> No proper planning
Example:
A small student project
Start coding directly
Requirements may change anytime

Understanding IP Address in Simple Terms

Vidya — Sat, 11 Apr 2026 16:48:34 +0000

What is an IP Address?
An IP address (Internet Protocol address) is a unique number given to every device connected to a network (like the internet).
Example
When you visit Google, your device uses an IP address like:
142.250.183.14 to connect to Google’s server.

Types of IP Address
1.IPv4 (common)
Example: 192.168.1.1
2. IPv6 (newer)
Example: 2405:201:abcd::1

Why it is used?
--> To identify devices
--> To send and receive data
--> To connect websites and users

To find the IP address of Google, you can use a few simple methods:
1. Using Command Prompt (Windows)
Open Command Prompt
Type:
ping google.com
You’ll see output like:
Reply from 142.250.183.14

--> That number is Google’s IP address.
2. Using nslookup (Windows / Linux / Mac)
nslookup google.com
Output:
Address: 142.250.xxx.xxx
3. Using Terminal (Linux / Mac)
dig google.com
or
host google.com

Important Note
Google doesn’t have one fixed IP address.
It uses many IPs (like 142.250.x.x, 172.217.x.x) depending on your location and server.

Self Introduction

Vidya — Fri, 10 Apr 2026 16:00:03 +0000

Myself Vidya P. I completed my Bachelor’s degree in 2022 with a specialization in Electronics and Communication Engineering (ECE).
After my graduation, I received an offer from Infosys in 2022. However, I had to wait for around 1.5 years for onboarding. During that period,I explored opportunities in various companies, but I was unable to secure a role, as I was mostly waiting for onboarding.
Later, I joined Infosys as a System Engineer Trainee in Mysuru. During my training, I learned Java and DBMS. As part of the evaluation process, we had to clear an internal exam to get project allocation. Although I worked hard, I was not able to clear that exam.
Instead of giving up, I took it as a learning opportunity. I decided to strengthen my technical skills at an advanced level and joined Payilagam to pursue a Java Full Stack Developer course.
As part of my learning, I have developed several frontend projects using React JS, including clones of Instagram, Facebook, and Google, as well as a quiz application and a product card project.
These experiences have improved my confidence and technical abilities. I strongly believe that I can contribute effectively and grow as a developer.