DEV Community: Vidya

Spring vs Spring Boot – Complete Comparison

Vidya — Tue, 12 May 2026 15:33:31 +0000

What is Spring?
=> Spring Framework is a Java framework used to build enterprise applications.
=> It provides features like Dependency Injection (DI), IoC, database handling, security, and web development.
=> In Spring, developers must configure many things manually using XML or Java configuration.
=> It is flexible and powerful but requires more setup and coding.
Spring is mainly used for large-scale Java applications.
Example: Creating web applications, banking systems, REST APIs, and microservices.

What is Spring Boot?
=> Spring Boot is built on top of Spring Framework.
=> It reduces configuration work and makes development faster and easier.
=> Spring Boot provides auto-configuration, embedded servers, and starter dependencies.
=> You can run applications directly without deploying WAR files manually.
=> It follows “convention over configuration,” so less code is needed.
Example: Quickly creating REST APIs, backend services, and microservice applications.

Why do we use Spring Boot Framework in Java instead of others?
=> Spring Boot makes Java development simple, fast, and production-ready.
=> It has built-in support for REST APIs, databases, security, and microservices.
=> Embedded servers like Tomcat help run applications easily.
=> Large community support and many companies use it in real projects.
=> It reduces boilerplate code and saves development time.
=> Compared to many frameworks, Spring Boot is easier for creating scalable enterprise applications quickly.

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Reverse Words in a Sentence

Vidya — Fri, 08 May 2026 04:38:25 +0000

JavaScript Program:

let sentence = "how are you";
let end = sentence.length - 1; 
let word = "";
let start;
for (let i = end; i >= 0; i--) {
  if (sentence[i] === " " || i === 0) {

    let start;

    if (i === 0) {
      start = i;      
    } else {
      start = i + 1;
    }

    for (let j = start; j <= end; j++) {
      word = word + sentence[j];
    }
    console.log(word);
    word = "";
    end = i - 1;  
  }
}

output:

Algorithm:

Start
Initialize a string sentence = "how are you"
Set: end = length of sentence - 1 word = "" (empty string)
Loop from end to start of the string (i = end → 0)
For each character: Check if space OR i == 0
If condition is true: Determine start index: If i == 0 → start = i Else → start = i + 1
Extract the word: Loop from start → end Add each character to word
Print the word
Reset: word = "" end = i - 1
Continue loop until i = 0
Stop

Maven in Spring Boot

Vidya — Tue, 05 May 2026 15:08:44 +0000

What is Maven?
=> Maven is a build automation and project management tool mainly used for Java applications, developed by Apache Software Foundation. It uses a file called pom.xml (Project Object Model) to define project details, dependencies, and build configuration.

=> Maven automatically downloads required libraries from online repositories, so developers don’t need to manage JAR files manually. It follows a standard project structure, making projects easy to understand and maintain.

=> Maven also manages the build lifecycle, including compile, test, package, and deploy phases. Overall, Maven simplifies development by handling dependencies, builds, and project consistency efficiently.

For example, if you add spring-boot-starter-web dependency in pom.xml, Maven will automatically download all required libraries and help you run your Spring Boot REST API easily.

Why We Used?
=> We use Maven (Apache Maven) because it simplifies project development by automating repetitive tasks and managing dependencies efficiently. Instead of manually downloading and adding JAR files, Maven automatically fetches required libraries from repositories.

=> It ensures a standard project structure, making code easier to understand and maintain across teams. Maven also handles the full build lifecycle like compiling, testing, packaging, and deploying with simple commands.

=> This reduces errors and saves time, especially in large projects. Overall, Maven improves productivity, consistency, and project management in Java applications.

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MVC Architecture Flow in Spring Boot

Vidya — Tue, 05 May 2026 08:05:26 +0000

What is MVC?
MVC stands for:

M → Model
V → View
C → Controller

It is a design pattern used to organize your code by separating concerns.

=> In Spring Boot, MVC helps structure web applications cleanly.

MVC in Spring Boot is a design pattern that separates an application into Model, View, and Controller. The Model handles data and business logic, while the View is responsible for displaying the user interface. The Controller acts as a bridge, receiving user requests and coordinating between Model and View. When a request comes in, the Controller processes it, interacts with the Model, and sends the result to the View. This separation keeps the code organized and easier to maintain. Overall, MVC improves scalability, readability, and development efficiency in web applications.

Why MVC is Used?

Without MVC, all code (logic + UI + data) gets mixed → messy

With MVC:
✔ Code is clean and organized
✔ Easy to maintain & debug
✔ Supports team development
✔ Reusable components

Components of MVC

1.Model (Data Layer)

Represents data + business logic
Usually includes:
=> Entity classes
=> Database interaction

Example:

class Student {
    int id;
    String name;
}

2.View (UI Layer)

What the user sees 👀
Can be:
-> HTML
-> JSP
-> Thymeleaf

Example:

<h1>Welcome Student</h1>
<p th:text="${name}"></p>

3.Controller (Request Handler)

=> Handles user requests
=> Connects Model and View

Example:

@RestController
public class StudentController {

    @GetMapping("/student")
    public String getStudent() {
        return "Hello Student";
    }
}

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Map in Java

Vidya — Sat, 02 May 2026 04:49:16 +0000

What is Map in Java Collections?
A Map in Java (from Java Collections Framework) is a data structure that stores data in key–value pairs.

Each key is unique
Each value is mapped to a key
Think of it like a dictionary: word → meaning

Example:
101 → "John"
102 → "Alice"

Why do we use Map?
We use a Map when:

--> We need fast lookup using a key
--> We want to store pairs of related data
--> We need unique keys

Real-world examples:

Student ID → Name
Username → Password
Product ID → Price

Common Map Implementations
HashMap → Fast, unordered
LinkedHashMap → Maintains insertion order
TreeMap → Sorted by keys

Important Methods

put(key, value) → Insert data
get(key) → Get value
remove(key) → Delete
containsKey(key) → Check key
keySet() → Get all keys

Difference between Map vs List vs Set?

Set in Java

Vidya — Thu, 30 Apr 2026 14:57:49 +0000

What is a Set in Java Collections?
A Set is a collection in Java that:
--> Does not allow duplicate elements
--> Does not guarantee index (no ordering like List)
--> Stores only unique values

It is part of java.util.Set interface.

Main Types of Set
1. HashSet
--> No order maintained
--> Fast performance
--> Allows one null

Example

import java.util.*;

public class HashSetExample {
    public static void main(String[] args) {
        Set<String> set = new HashSet<>();

        set.add("Apple");
        set.add("Banana");
        set.add("Apple"); // duplicate ignored
        set.add("Mango");

        System.out.println(set);
    }
}      output:[Apple, Banana, Mango]

2. LinkedHashSet
--> Maintains insertion order
--> No duplicates allowed
Example

import java.util.*;

public class LinkedHashSetExample {
    public static void main(String[] args) {
        Set<Integer> set = new LinkedHashSet<>();

        set.add(10);
        set.add(30);
        set.add(20);
        set.add(10); // ignored

        System.out.println(set);
    }
}         output:[10, 30, 20]

3. TreeSet
--> Stores elements in sorted (ascending) order
--> No duplicates allowed
--> Slower than HashSet

Example:

 import java.util.*;

public class TreeSetExample {
    public static void main(String[] args) {
        Set<Integer> set = new TreeSet<>();

        set.add(50);
        set.add(10);
        set.add(30);
        set.add(20);

        System.out.println(set);
    }
}         output:[10, 20, 30, 50]

Key Features of Set
--> Unique elements only
--> No index (no get(0) like List)
--> Used in removing duplicates
--> Supports iteration (for-each loop)

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