DEV Community: SILAMBARASAN A

EMIRP

SILAMBARASAN A — Sun, 05 Apr 2026 14:00:15 +0000

Emirp Number – Explanation

What is an Emirp Number?

An Emirp number is a special type of prime number.

Conditions:

The number itself must be prime
Its reverse must also be prime
The reversed number should be different from the original

Example:

17 → Prime
Reverse (71) → Prime
17 ≠ 71 → Valid Emirp

So, 17 is an Emirp number

PYTHON :

def prime(no):
    div=2
    while div < no/2:
        if no % div == 0:
            return False
        div += 1
    return True

def reverse(no):
    rev = 0
    while no > 0:
        rev = rev * 10 + no % 10
        no = no // 10
    return rev

num = 17

if prime(num) and prime(reverse(num)):
    print(num, "is emirp")
else:
    print(num, "is not emirp")

Start
↓
Take number (17)
↓
Check if prime → YES
↓
Reverse number → 71
↓
Check reverse is prime → YES
↓
Both true → Emirp number
↓
End

JAVA SCRIPT CODE :

function prime(no) {
    let div = 2;

    while (div < no / 2) {
        if (no % div === 0) {
            return false;
        }
        div++;
    }
    return true;
}

function reverse(no) {
    let rev = 0;

    while (no > 0) {
        rev = rev * 10 + (no % 10);
        no = Math.floor(no / 10);
    }
    return rev;
}

let num = 17;

if (prime(num) && prime(reverse(num))) {
    console.log(num + " is emirp");
} else {
    console.log(num + " is not emirp");
}

JAVA CODE :

public class EmirpNumber {

    // Function to check prime
    static boolean prime(int no) {
        int div = 2;

        while (div < no / 2) {
            if (no % div == 0) {
                return false;
            }
            div++;
        }
        return true;
    }

    // Function to reverse number
    static int reverse(int no) {
        int rev = 0;

        while (no > 0) {
            rev = rev * 10 + (no % 10);
            no = no / 10;
        }
        return rev;
    }

    public static void main(String[] args) {
        int num = 17;

        if (prime(num) && prime(reverse(num))) {
            System.out.println(num + " is emirp");
        } else {
            System.out.println(num + " is not emirp");
        }
    }
}

NEON, STRONG, PERFECT

SILAMBARASAN A — Fri, 03 Apr 2026 12:42:13 +0000

NEON :

Neon Number

A Neon Number is a number where:

Sum of digits of its square = the number itself

Formula Idea:

Take the number
Find its square
Add the digits of the square
If result = original number → Neon Number

Example :

Number = 9

Square → 9 × 9 = 81
Sum of digits → 8 + 1 = 9

Result = 9 → Neon Number

PYTHON :

def neon(n):
    fact=n*n
    sum=0
    while fact>0:
        sum=sum+fact%10
        fact=fact//10
    if(n==sum):
        print(n," is neno")
    else:
        print(n," is not neno")
print(neon(9))

JAVA SCRIPT :

function neon(n) {
    let fact = n * n;
    let sum = 0;

    while (fact > 0) {
        sum = sum + (fact % 10);
        fact = Math.floor(fact / 10);
    }

    if (n === sum) {
        console.log(n + " is neon");
    } else {
        console.log(n + " is not neon");
    }
}

neon(9);

JAVA :

public class NeonNumber {

    public static void neon(int n) {
        int fact = n * n;
        int sum = 0;

        while (fact > 0) {
            sum = sum + (fact % 10);
            fact = fact / 10;  // integer division
        }

        if (n == sum) {
            System.out.println(n + " is neon");
        } else {
            System.out.println(n + " is not neon");
        }
    }

    public static void main(String[] args) {
        neon(9);
    }
}

OUTPUT :

Strong Number :

A Strong Number is a number where:

Sum of factorial of each digit = the number itself

Formula Idea:

Take the number
Separate each digit
Find factorial of each digit
Add all factorials
If result = original number → Strong Number

Example :

Number = 145

Digits → 1, 4, 5
Factorials →
- 1! = 1
- 4! = 24
- 5! = 120
Sum → 1 + 24 + 120 = 145

Result = 145 → Strong Number

PYTHON :

def factorial(n):
    if n==1:
        return 1
    return n*factorial(n-1)

def strong(num):
    numc=num
    sum=0
    while  numc>0:
        sum=sum+factorial(numc%10)
        numc=numc//10
    if sum==num:
        print( num," is strong")
    else:
        print( num," is not strong")

strong(145)

JAVA SCRIPT :

function factorial(n) {
    if (n === 0 || n === 1) {
        return 1;
    }
    return n * factorial(n - 1);
}

function strong(num) {
    let numc = num;
    let sum = 0;

    while (numc > 0) {
        let digit = numc % 10;
        sum = sum + factorial(digit);
        numc = Math.floor(numc / 10);
    }

    if (sum === num) {
        console.log(num + " is strong");
    } else {
        console.log(num + " is not strong");
    }
}

strong(145);

JAVA :

public class StrongNumber {

    // Factorial function (recursion)
    public static int factorial(int n) {
        if (n == 0 || n == 1) {
            return 1;
        }
        return n * factorial(n - 1);
    }

    // Strong number check
    public static void strong(int num) {
        int numc = num;
        int sum = 0;

        while (numc > 0) {
            int digit = numc % 10;
            sum = sum + factorial(digit);
            numc = numc / 10;
        }

        if (sum == num) {
            System.out.println(num + " is strong");
        } else {
            System.out.println(num + " is not strong");
        }
    }

    public static void main(String[] args) {
        strong(145);
    }
}

OUTPUT :

Perfect Number – Definition

A Perfect Number is a number where:

Sum of its proper divisors = the number itself

What are Proper Divisors?

All positive divisors of a number excluding the number itself

Example :

Number = 6

Divisors → 1, 2, 3
Sum → 1 + 2 + 3 = 6 Result = 6 → Perfect Number

PYTHON :

def divisor(n):
    div=1
    divsum=0
    while div<=n/2:
        if n%div==0:
            divsum=divsum+div
        div+=1
    if n==divsum:
        print(n," is perfect")
    else:
        print(n," is not perfect")
divisor(6)

JAVA SCRIPT :

function divisor(n) {
    let div = 1;
    let divsum = 0;

    while (div <= Math.floor(n / 2)) {
        if (n % div === 0) {
            divsum = divsum + div;
        }
        div++;
    }

    if (n === divsum) {
        console.log(n + " is perfect");
    } else {
        console.log(n + " is not perfect");
    }
}

divisor(6);

JAVA :

public class PerfectNumber {

    public static void divisor(int n) {
        int div = 1;
        int divsum = 0;

        while (div <= n / 2) {
            if (n % div == 0) {
                divsum = divsum + div;
            }
            div++;
        }

        if (n == divsum) {
            System.out.println(n + " is perfect");
        } else {
            System.out.println(n + " is not perfect");
        }
    }

    public static void main(String[] args) {
        divisor(6);
    }
}

OUTPUT :

Odd-Even Digit Rearrangement

SILAMBARASAN A — Thu, 02 Apr 2026 18:38:38 +0000

div → Used to extract digits
num → Used to check position (odd or even)
rev1 → Stores digits from odd positions
rev2 → Stores digits from even positions

PYTHON CODE :

div=100000
num=1
rev1=0
rev2=0
no=892581
while div>0:
    res=no//div
    if num%2!=0:
        rev1=rev1*10+res%10
    else:
        rev2=rev2*10+res%10
    div=div//10
    num+=1
print(rev1*1000+rev2)

OUTPUT :

Loop Execution

Iteration 1:
res = 892581 // 100000 = 8
num = 1 (odd)

rev1 = 0*10 + 8 = 8

Iteration 2:
res = 892581 // 10000 = 89 → last digit = 9
num = 2 (even)

rev2 = 0*10 + 9 = 9

Iteration 3:
res = 892581 // 1000 = 892 → last digit = 2
num = 3 (odd)

rev1 = 8*10 + 2 = 82

Iteration 4:
res = 892581 // 100 = 8925 → last digit = 5
num = 4 (even)

rev2 = 9*10 + 5 = 95

Iteration 5:
res = 892581 // 10 = 89258 → last digit = 8
num = 5 (odd)

rev1 = 82*10 + 8 = 828

Iteration 6:
res = 892581 // 1 = 892581 → last digit = 1
num = 6 (even)

rev2 = 95*10 + 1 = 951

JAVA SCRIPT :

let div = 100000;
let num = 1;
let rev1 = 0;
let rev2 = 0;
let no = 892581;

while (div > 0) {
    let res = Math.floor(no / div);

    if (num % 2 !== 0) {
        rev1 = rev1 * 10 + (res % 10);
    } else {
        rev2 = rev2 * 10 + (res % 10);
    }

    div = Math.floor(div / 10);
    num++;
}

console.log(rev1 * 1000 + rev2);

Number Reversal and Rotation using Recursion

SILAMBARASAN A — Thu, 02 Apr 2026 16:55:31 +0000

INPUT → 123456
OUTPUT → 654321

PYTHON :

def sum1(no,reverse=0):
    if no>0:
        reverse=reverse*10+no%10
        no=no//10
        return sum1(no,reverse)
    return reverse
print(sum1(123437))

INPUT → 123456

OUTPUT → 563412

no % 100
→ Gets the last 2 digits of the number

reverse * 100
→ Creates space to add new digits at the end

Math.floor(no / 100)
→ Removes the last 2 digits from the number

PYTHON :

def sum1(no,reverse=0):
    if no>0:
        reverse=reverse*100+no%100
        no=no//100
        return sum1(no,reverse)
    return reverse
print(sum1(123456))

JAVA SCRIPT :

function sum1(no, reverse = 0) {
    if (no > 0) {
        reverse = reverse * 100 + (no % 100);
        no = Math.floor(no / 100);
        return sum1(no, reverse);
    }
    return reverse;
}

console.log(sum1(123456));

JAVA :

class Main {

    static int sum1(int no, int reverse) {
        if (no > 0) {
            reverse = reverse * 100 + (no % 100);
            no = no / 100;
            return sum1(no, reverse);
        }
        return reverse;
    }

    public static void main(String[] args) {
        System.out.println(sum1(123456, 0)); // Output: 563412
    }
}

OUTPUT :

INPUT → 123456

OUTPUT → 456123

no % 1000
→ Gets the last 3 digits of the number

reverse * 1000
→ Creates space to add new digits at the end

Math.floor(no / 1000)
→ Removes the last 3 digits from the number

PYTHON :

def sum1(no,reverse=0):
    if no>0:
        reverse=reverse*1000+no%1000
        no=no//1000
        return sum1(no,reverse)
    return reverse
print(sum1(123456))

JAVA SCRIPT :

function sum1(no, reverse = 0) {
    if (no > 0) {
        reverse = reverse * 1000 + (no % 1000);
        no = Math.floor(no / 1000);
        return sum1(no, reverse);
    }
    return reverse;
}

console.log(sum1(123456));

JAVA :

class Main {

    static int sum1(int no, int reverse) {
        if (no > 0) {
            reverse = reverse * 1000 + (no % 1000);
            no = no / 1000;
            return sum1(no, reverse);
        }
        return reverse;
    }

    public static void main(String[] args) {
        System.out.println(sum1(123456, 0)); // Output: 563412
    }
}

OUTPUT :

Static vs Non-Static in JAVA

SILAMBARASAN A — Thu, 02 Apr 2026 15:53:00 +0000

Static vs Non-Static in Java

When learning Java, one very important concept is Static vs Non-Static (Instance).
If you understand this clearly, Java and OOP will become much easier.

What is Static?

static is a keyword used to create variables or methods that belong to the class, not to objects.

Example:

class Student {
    static String college = "ABC College";
}

Access:
System.out.println(Student.college);

Key Idea:

Only one copy is created
Shared by all objects
No need to create an object

What is Non-Static? (Instance)

Non-static means it belongs to an object (instance).

Example:

class Student {
    int id;
    String name;
}

Access:

Student s1 = new Student();
s1.id = 101;
s1.name = "Ram";

Key Idea:

Each object has its own copy
Must create an object to use it

✔️ rollNo, name → Non-static
✔️ college → Static

When to Use Static?

Use static when data is common for all objects:

Shared values
Utility methods
Constants

When to Use Non-Static?

Use non-static when data is different for each object:

Student name
Employee salary
Product details

Important Rule

A static method cannot directly access non-static variables

Wrong:

class Test {
    int x = 10;

    static void show() {
        System.out.println(x); // Error
    }
}

Correct:

class Test {
    int x = 10;

    static void show() {
        Test obj = new Test();
        System.out.println(obj.x);
    }
}

Real-Life Example

College System

class Student {
    int rollNo;                 // Unique for each student
    String name;                // Unique for each student
    static String college = "ABC"; // Same for all students
}

rollNo, name → Non-static
college → Static

DECIMAL NUMBERS

SILAMBARASAN A — Wed, 01 Apr 2026 17:51:31 +0000

Decimal – Simple Definition

A decimal number is a number written using the base-10 system.

Decimal Numbers – Basic Idea

To break a decimal number (example: 2345) into digits:

no % 10 → gets the last digit
no // 10 → removes the last digit

This is the main logic used in all programs

SUM OF DIGITS

What does it do?
It adds all the digits in a number

Example:
2345 → 2 + 3 + 4 + 5 = 14

Loop Method

We use a while loop to add digits one by one

SUM OF DIGITS IN LOOP :

no=2345
sum=0
while no>0:
    sum=sum+no%10
    no=no//10
print(sum)

OUTPUT :
14

Recursion Method

The function calls itself again and again to repeat the process

SUM OF DIGITS IN RECURSION :

def sum1(no,sum):
    if no>0:
        sum=sum+no%10
        no=no//10
        return sum1(no,sum)
    return sum
print(sum1(1234,0))

OUTPUT :
10

COUNT OF DIGIT

What does it do?

It counts how many digits are in a number

Example:
2345 → 4 digits

Loop Method

In each step, we do count += 1

COUNT OF DIGITS IN LOOP :

no=2345
count=0
while no>0:
    count+=1
    no=no//10
print(count)

OUTPUT :
4

COUNT OF DIGITS IN RECURSION :

Recursion Method

Idea:

count = 1 + count of remaining digits

def sum1(no,count):
    if no>0:
        count+=1
        no=no//10
        return sum1(no,count)
    return count
print(sum1(123437,0))

OUTPUT :
6

NUMBER REVERSE

What does it do?

It reverses the number

Example:
2345 → 5432

Loop Method

reverse = reverse * 10 + last digit

NUMBER REVERSE IN LOOP :

no=2345
reverse=0
while no>0:
    reverse=reverse*10+no%10
    no=no//10
print(reverse)

OUTPUT :
5432

NUMBER REVERSE IN RECURSION :

Recursion Method

Idea:
Take the last digit and build a new number step by step

def sum1(no,reverse):
    if no>0:
        reverse=reverse*10+no%10
        no=no//10
        return sum1(no,reverse)
    return reverse
print(sum1(123437,0))

OUTPUT :
734321

Primitive Data Types in Java

SILAMBARASAN A — Wed, 01 Apr 2026 16:31:10 +0000

in Java, primitive data types are the most basic types of data. They store simple values (not objects) and are very fast.

1. byte

Size: 1 byte (8 bits)
Range: -128 to 127
Used to save memory in large arrays

Example:
byte b = 100;

2. short

Size: 2 bytes
Range: -32,768 to 32,767

Example:
short s = 20000;

3. int

Size: 4 bytes
Most commonly used
Range: -2³¹ to 2³¹-1

Example:
int num = 100000;

4. long

Size: 8 bytes
Used for very large numbers

Example:
long l = 10000000000L;

5. float

Size: 4 bytes
Decimal numbers (less precision)

Example:
float f = 5.75f;

6. double

Size: 8 bytes
More precise decimal values

Example:
double d = 19.99;

7. char

Size: 2 bytes
Stores single character

Example:
char c = 'A';

8. boolean

Size: 1 bit (logical)
Values: true / false

Example:
boolean isJavaFun = true;

Simple Summary Table

Type	Size	Example
byte	1 byte	100
short	2 bytes	20000
int	4 bytes	100000
long	8 bytes	10000000000L
float	4 bytes	5.75f
double	8 bytes	19.99
char	2 bytes	'A'
boolean	1 bit	true

OOPS

SILAMBARASAN A — Wed, 01 Apr 2026 05:33:29 +0000

Object-Oriented Programming (OOP) is one of the most widely used programming paradigms in modern software development. It helps developers design applications in a structured, reusable, and scalable way.

Instead of focusing only on functions and logic, OOP organizes programs around objects and data, making real-world problems easier to model.

What is OOP?

Object-Oriented Programming is a programming approach where everything is treated as an object. These objects interact with each other to perform tasks.

Think of it like real life:

A car is an object
It has properties like color, speed
And behaviors like start, stop

OOP follows the same idea in programming.

Core Concepts of OOP

1. Class

A class is like a blueprint or template.

It defines:

What properties an object will have
What actions it can perform

Example (real life):
A "Car" blueprint that describes features like color, engine, and speed.

2. Object

An object is an instance of a class.

It represents a real-world entity created using a class.

Example:
If "Car" is a class, then:

A red car
A blue car

These are objects.

3. Encapsulation

Encapsulation means wrapping data and methods together into a single unit.

It also ensures data hiding, meaning:

Sensitive data is protected
Access is controlled

Real-life example:
A mobile phone — you use apps without knowing the internal hardware details.

4. Abstraction

Abstraction means showing only essential details and hiding complexity.

Example:
When you drive a car:

You use steering, brake, accelerator
You don’t need to know how the engine works internally

This makes systems easier to use.

5. Inheritance

Inheritance allows one class to reuse properties and behaviors of another class.

Example:

A "Vehicle" class
"Car" and "Bike" can inherit from it

This promotes:

Code reuse
Better organization

6. Polymorphism

Polymorphism means one thing can take many forms.

Example:

A person can be a student, employee, or teacher
Same person, different roles

In programming, it allows:

Same method name
Different behavior based on context

RECURSION SUMS

SILAMBARASAN A — Tue, 31 Mar 2026 20:02:43 +0000

1. PRINT 1 to 5

PYTHON CODE:

def fact(i):
    if i<=5:
        print(i)
        i+=1
        fact(i)
fact(1)

🔁 Simple Flow

fact(1)
→ print 1
→ fact(2)

fact(2)
→ print 2
→ fact(3)

fact(3)
→ print 3
→ fact(4)

fact(4)
→ print 4
→ fact(5)

fact(5)
→ print 5
→ fact(6)

fact(6)
→ stop ❌`

🧾 Output

1
2
3
4
5

2. ODD NUMBERS PRINT: 1 3 5 7

PYTHON CODE :

def fact(i):
if i<=15:
if i%2!=0:
print(i)
i+=1
fact(i)
fact(1)

🔁 Simple Flow
fact(1)
→ 1 is odd → print 1
→ call fact(2)

fact(2)
→ not odd ❌
→ call fact(3)

fact(3)
→ print 3
→ call fact(4)

fact(4)
→ skip
→ call fact(5)

...

👉 continues same until 15

fact(15)
→ print 15
→ call fact(16)

fact(16)
→ stop ❌

🧾 Output
1 3 5 7 9 11 13 15

3. FACTORIAL :

Factorial meaning:

5! = 5 × 4 × 3 × 2 × 1 = 120

PYTHON CODE :
def factorial(n):
if n == 0 or n == 1:
return 1
return n * factorial(n - 1)
print(factorial(5))

🔁 Simple Flow
factorial(5)
→ 5 * factorial(4)

factorial(4)
→ 4 * factorial(3)

factorial(3)
→ 3 * factorial(2)

factorial(2)
→ 2 * factorial(1)

factorial(1)
→ return 1 ✅ (stop)

🔙 Backward Calculation

factorial(2) = 2 * 1 = 2
factorial(3) = 3 * 2 = 6
factorial(4) = 4 * 6 = 24
factorial(5) = 5 * 24 = 120

🧾 Output

120

4. SUM OF N NUMBERS

✅ What this code does

👉 Finds sum of first n numbers

5 → 1 + 2 + 3 + 4 + 5 = 15

PYTHON CODE :

python def SUM(n): if n == 1: return 1 return n + SUM(n - 1) print(SUM(5))

🔁 Simple Flow

SUM(5)
→ 5 + SUM(4)

SUM(4)
→ 4 + SUM(3)

SUM(3)
→ 3 + SUM(2)

SUM(2)
→ 2 + SUM(1)

SUM(1)
→ return 1 ✅ (stop)

🔙 Backward Calculation

SUM(2) = 2 + 1 = 3
SUM(3) = 3 + 3 = 6
SUM(4) = 4 + 6 = 10
SUM(5) = 5 + 10 = 15

🧾 Output
15

5. COUNT DIVISORS

✅ What this code does

👉 Counts how many numbers divide num (except 1 and itself)

For 100:
👉 Divisors = 2, 4, 5, 10, 20, 25, 50
👉 Count = 7

PYTHON CODE :

python def count_divisors(num, div=2, count=0): if div > num // 2: return count if num % div == 0: count += 1 return count_divisors(num, div + 1, count) print(count_divisors(100))

🔍 How it Works

For num = 100:

Start div = 2
If divisible → increase count
Call function again with div + 1
Stops when div > 50

6. prime check

PYHTON CODE :

`python

def is_prime(num, div=2):
if div > num // 2:
return True
if num % div == 0:
return False
return is_prime(num, div + 1)
num = int(input("enter a number: "))
if num > 1 and is_prime(num):
print("This number is Prime")
else:
print("This number is not Prime")
`

🔁 How It Works (Simple)

Start checking from div = 2
If divisible → ❌ Not Prime
Else → call function with div + 1
Stops when div > num/2 → ✅ Prime

7. GCD

PYTHON CODE :

`python

def gcd(a, b):
if b == 0:
return a
return gcd(b, a % b)
print(gcd(10, 50))
`

🔥 Short Flow

gcd(10,50)
→ gcd(50,10)
→ gcd(10,0)
→ 10

🔁 Recursion Debugging Flow

SILAMBARASAN A — Mon, 30 Mar 2026 17:22:22 +0000

🔁 Recursion Debugging (Simple Explanation)

Recursion debugging means finding and fixing errors in a function that calls itself.

🧠 1. What happens in recursion?

Every recursive function must have:

✅ Base Case → stopping condition
🔁 Recursive Call → function calling itself

If something is wrong → program may:

❌ Run forever (infinite recursion)
❌ Give wrong output
❌ Crash (stack overflow)

🔍 2. Common Recursion Errors

❌ 1. Missing Base Case

def fact(n):
    return n * fact(n-1)

👉 Problem: No stopping condition → infinite loop

❌ 2. Wrong Base Case

def fact(n):
    if n == 0:
        return 0   # ❌ wrong
    return n * fact(n-1)

👉 Factorial of 0 should be 1, not 0

❌ 3. Wrong Recursive Call

def fact(n):
    if n == 1:
        return 1
    return n * fact(n+1)   # ❌ wrong direction

👉 It should reduce n, not increase

❌ 4. Stack Overflow (Too deep recursion)

def loop(n):
    return loop(n+1)

👉 Never stops → crash

🧠 Code Understanding

def fact(i, a):
    if i <= 5:
        a = a * i
        return fact(i + 1, a)
    return a

print(fact(1, 1))

Meaning:
i → current number
a → accumulated result (answer store panra variable)

🔁 Step-by-Step Flow
📍 Initial Call
fact(1, 1)

🔽 Call Phase (Going Down)

i=1, a=1 → a = 1*1 = 1 → fact(2, 1)
i=2, a=1 → a = 1*2 = 2 → fact(3, 2)
i=3, a=2 → a = 2*3 = 6 → fact(4, 6)
i=4, a=6 → a = 6*4 = 24 → fact(5, 24)
i=5, a=24 → a = 24*5 = 120 → fact(6, 120)

🔼 Return Phase (Coming Back)

👉 Important:
This is tail recursion, so no pending calculations

fact(6,120) → 120
fact(5,24) → 120
fact(4,6) → 120
fact(3,2) → 120
fact(2,1) → 120
fact(1,1) → 120

🎯 Final Output
120

📊 Simple Flow Diagram

embed fact(1,1)
↓
fact(2,1)
↓
fact(3,2)
↓
fact(4,6)
↓
fact(5,24)
↓
fact(6,120) → return 120

Java Features

SILAMBARASAN A — Mon, 30 Mar 2026 16:19:45 +0000

Java is a high-level, object-oriented programming language. This language is very easy to learn and widely used. It is known for its platform independence, reliability, and security. It follows one principle, that is "Write Once, Run Anywhere" principle. It supports various features like portability, robustness, simplicity, multithreading, and high performance, which makes it a popular choice for beginners as well as for developers.

1. Simple Syntax (Java)

Java is designed to be easy to read, write, and understand, especially for beginners.

🔹 Why Java syntax is simple?

✔️ Similar to C/C++ → easy for beginners with basic programming knowledge
✔️ No complicated features like:
- Pointers ❌
- Operator overloading ❌
✔️ Clear and structured code style
✔️ Uses English-like keywords (class, public, static, void)

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

🔍 Explanation (Easy):

public class Hello → class name
main() → starting point of program
System.out.println() → print output

2. Object-Oriented (Java)

Java is a pure Object-Oriented Programming (OOP) language (almost everything is based on objects).

🔹 What is Object-Oriented?

👉 Object-Oriented means writing programs using objects and classes instead of just functions.

Class → Blueprint (design)
Object → Real-world entity created from class

📌 Example:

Class = Car 🚗 (design)
Object = Your car (real instance)

Java is a pure object-oriented language. It supports core OOP concepts like,

Class
Objects
Inheritance
Encapsulation
Abstraction
Polymorphism

3. Platform Independent (Java)

Java is famous for “Write Once, Run Anywhere (WORA)” ✅

🔹 What does Platform Independent mean?

👉 A Java program written on one system (Windows/Linux/Mac) can run on any other system without changing the code.

🔄 How it works?

Java uses a special process:

1. Write code → .java file
2. Compile → converts to bytecode (.class)
3. Run on JVM → executes on any OS

🔁 Flow:

Java Code → Compiler → Bytecode → JVM → Output

4. Interpreted (Java)

Java is both compiled + interpreted language ✅

🔹 What does “Interpreted” mean?

👉 An interpreted language executes code line by line instead of running fully compiled machine code.

🔄 How Java is Interpreted?

Java works in 2 steps:

1. Compilation

java → converted into bytecode (.class) using compiler

2. Interpretation (JVM)

JVM reads bytecode line by line
Converts it into machine code and runs it

🔁 Flow:

Java Code → Compiler → Bytecode → JVM (Interpreter) → Output

5. Scalable (Java)

👉 Scalable means a program can handle growth (more users, more data, more features) without breaking.

🔹 Simple Real-Life Example

📱 Think about a food delivery app:

Initially → 10 users
Later → 10,000 users 👉 If the app is scalable, it will still work smoothly even when users increase.

6. Portable (Java)

👉 Portable means Java programs can run on different systems without changing code or behavior.

🔹 What is Portability?

👉 A program written on one machine can be moved (ported) to another system and still work the same.

🔄 Why Java is Portable?

✔️ Uses standard data types (same size everywhere)
✔️ No system-dependent features (like pointers)
✔️ Bytecode runs on any JVM

7. Secured and Robust (Java)

Java is designed to be both secure 🔐 and robust 💪, making it reliable for real-world applications.

🔐 Security in Java

👉 Java protects systems from harmful code.

🔹 How Java is Secure?

✔️ No pointers → prevents direct memory access
✔️ JVM Security → runs code inside a safe environment (sandbox)
✔️ Bytecode verification → checks code before execution
✔️ Exception handling → prevents system crashes

💪 Robust in Java

👉 Robust means strong and reliable, even when errors occur.

🔹 Why Java is Robust?

- ✔️ Strong memory management
- ✔️ Automatic Garbage Collection
- ✔️ Exception handling system
- ✔️ Type checking (compile + runtime)

8. Memory Management (Java)

👉 Java handles memory automatically, so developers don’t need to manage it manually like in C/C++.

🔹 What is Memory Management?

👉 It is the process of:

Allocating memory 🧠
Using memory
Releasing unused memory

🔄 How Java Manages Memory?

Java uses Heap Memory + Stack Memory + Garbage Collector

9. High Performance (Java)

👉 Java is considered high performance because it runs fast compared to many other high-level languages.

🔹 Why Java is High Performance?

🚀 1. JIT Compiler (Just-In-Time)

👉 Converts bytecode into machine code at runtime

Frequently used code → optimized
Runs faster after few executions

⚡ 2. Bytecode Optimization

👉 Java compiles code into bytecode, which is:

Efficient
Optimized for execution

🧵 3. Multithreading Support

👉 Java can run multiple tasks at the same time
👉 Improves overall performance

♻️ 4. Efficient Memory Management

👉 Garbage Collector removes unused objects
👉 Prevents memory issues and improves speed

10. Multithreading (Java)

👉 Multithreading means running multiple tasks at the same time within a single program.

🔹 What is a Thread?

👉 A thread is a small unit of a process
👉 Java allows multiple threads to run concurrently

🔄 Real-Life Example

📱 Mobile phone:

Listening to music 🎧
Downloading file ⬇️
Using WhatsApp 💬

👉 All happening at the same time → Multithreading

11. Rich Standard Library (Java)

👉 Java has a huge collection of built-in classes and packages
👉 So you don’t need to write everything from scratch ✅

🔹 What is Standard Library?

👉 It is a collection of ready-made code provided by Java
👉 You can directly use it in your programs

📦 Example packages:

java.lang → basic features
java.util → collections (ArrayList, HashMap)
java.io → file handling
java.net → networking

12. Functional Programming Features (Java) – Simple Explanation

👉 From Java 8, Java supports Functional Programming (FP) concepts
👉 This helps you write short, clean, and modern code ✅

🔹 What is Functional Programming?

👉 Instead of writing long code, you write small functions and pass them around

👉 Focus on:

What to do ✔️
Not how to do ❌

13. Integration with Other Technologies (Java)

👉 Java can easily connect and work with other technologies like databases, web apps, APIs, and different programming languages.

🔹 What is Integration?

👉 Integration means:
➡️ Java can communicate with other systems
➡️ Share data and work together

14. Support for Mobile and Web Applications (Java)

👉 Java is widely used to build both mobile apps 📱 and web applications 🌐

📱 1. Mobile Applications (Android)

👉 Java is one of the main languages for Android app development

Used in Android Studio
Builds apps like:
- WhatsApp 💬
- Instagram 📸
- Banking apps 🏦

🌐 2. Web Applications

👉 Java is used to build backend (server-side) of websites

Technologies:
- Servlet
- JSP
- Spring Boot

👉 Used in:

Login systems 🔐
E-commerce sites 🛒
Online booking systems 🎟️

15. Documentation and Community Support (Java)

👉 Java has good learning materials and many people to help you ✅

📚 Documentation

👉 Java gives official guides with:

Easy explanations
Examples
Ready reference (API)

👉 You can learn how to use classes like ArrayList, Scanner easily

👨‍💻 Community Support

👉 Many developers use Java, so help is everywhere:

Stack Overflow
YouTube
GitHub
Blogs

👉 If you get an error → just search → solution available 😄

RECURSION

SILAMBARASAN A — Sun, 29 Mar 2026 18:31:38 +0000

🔁 What is Recursion?

👉 Recursion means:

A function calls itself to solve a problem.

💡 Simple Definition:

👉 “A function solving a problem by calling itself again and again until a condition is met.”

Print 1 to 5

PYTHON CODE:

def fact(i):
    if i<=5:
        print(i)
        i+=1
        fact(i)
fact(1)

OUTPUT :

JAVA CODE :

public class Home {

    public static void fact(int i) {
        if (i <= 5) {
            System.out.println(i);
            i++;
            fact(i);
        }
    }

    public static void main(String[] args) {
        fact(1);
    }
}

OUTPUT :

JAVA SCRIPT :

function fact(i) {
            if (i <= 5) {
                console.log(i);
                i++;
                fact(i);
            }
        }

        fact(1);

OUTPUT :

ODD NUMBERS PRINT: 1 3 5 7

JAVA CODE :

public class Home {

    public static void fact(int i) {
        if (i <= 10) {
            if (i%2!=0){
                System.out.println(i);
            }
            i++;
            fact(i);
        }
    }

    public static void main(String[] args) {
        fact(1);
    }
}

OUTPUT :

PYHTON CODE :

def fact(i):
    if i<=15:
        if i%2!=0:
            print(i)
        i+=1
        fact(i)
fact(1)

OUTPUT :

JAVA SCRIPT :

function fact(i) {
            if (i <= 5) {
                if (i % 2 != 0) {
                    console.log(i);
                }
                i++;
                fact(i);
            }
        }

        fact(1);

OUTPUT :

PRINT 5 TABLE : 5 10 15 20 25

PYTHON :

def fact(i):
    if i<=21:
        if i%5==0:
            print(i)
        i+=1
        fact(i)
fact(1)

OUTPUT :

JAVA :

public class Home {

    public static void fact(int i) {
        if (i <= 20) {
            if (i%5==0){
                System.out.println(i);
            }
            i++;
            fact(i);
        }
    }

    public static void main(String[] args) {
        fact(1);
    }
}

OUTPUT :

JAVA SCRIPT :

function fact(i) {
            if (i <= 25) {
                if (i % 5 == 0) {
                    console.log(i);
                }
                i++;
                fact(i);
            }
        }

        fact(1);

OUTPUT :

FACTORIAL :

PYTHON :

def fact(i, a):
    if i <= 5:
        a = a * i
        return fact(i + 1, a)
    return a

print(fact(1, 1))

OUTPUT :

JAVA :

public class Home {

    public static int fact(int i, int a) {
        if (i <= 5) {
            a = a * i;
            return fact(i + 1, a);
        }
        return a;
    }

    public static void main(String[] args) {
        int result = fact(1, 1);
        System.out.println(result);
    }
}

OUTPUT :

JAVA SCRIPT :

function fact(i, a) {
            if (i <= 5) {
                a = a * i;
                return fact(i + 1, a);
            }
            return a;
        }

        let result = fact(1, 1);
        console.log(result);

OUTPUT :

SUM OF N NUMBERS :

PYTHON :

def fact(i, a):
    if i <= 10:
        a = a + i
        return fact(i + 1, a)
    return a

print(fact(1, 0))

OUTPUT :

JAVA SCRIPT :

function fact(i, a) {
            if (i <= 5) {
                a = a + i;
                return fact(i + 1, a);
            }
            return a;
        }

        let result = fact(1, 0);
        console.log(result);

OUTPUT :

JAVA :

public class Home {

    public static int fact(int i, int a) {
        if (i <= 5) {
            a = a + i;
            return fact(i + 1, a);
        }
        return a;
    }

    public static void main(String[] args) {
        int result = fact(1, 0);
        System.out.println(result);
    }
}

OUTPUT :