feat: Add PrimeNumbers program to print primes within a user-specified range

WHAT the code does:
Defines a PrimeNumbers class with:
- isPrime(int n): checks whether a number is prime by testing divisibility from 2 to n/2.
- main(): reads a start and end value from user input, iterates through the range, and prints prime numbers.

WHY this matters:
Provides a simple yet practical implementation of prime checking.
Demonstrates Scanner for interactive input and loops for range iteration.
Highlights algorithmic thinking: checking factors to classify numbers as prime or composite.
Useful as an educational program combining control flow, functions, and user interaction.

HOW it works:
User provides a starting and ending integer.
For each number in the range:
- isPrime(num) tests divisibility from 2 up to n/2.
- If no divisor is found, the number is printed as prime.
Example: input start=10, end=20 → output primes: 11 13 17 19.

Tips and gotchas:
The loop condition in isPrime should ideally be i <= sqrt(n) instead of n/2 for efficiency.
Current implementation treats numbers < 2 as prime (e.g., 0, 1) because no divisor is found; explicit checks are needed.
For larger ranges, this algorithm is inefficient compared to sieve-based approaches.
Always close the Scanner after use to release system resources.

Use-cases:
Educational demonstration of prime number algorithms and input handling.
Basic number theory exploration for beginners in Java.
Foundation for extending into optimized algorithms like Sieve of Eratosthenes.

Short key: class-primenumbers range-prime-check scanner-input.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section10Methods/src/PrimeNumbers.java

@@ -0,0 +1,29 @@
+import java.util.Scanner;
+
+public class PrimeNumbers {
+    static boolean isPrime(int n) {
+        for(int i = 2; i < n/2; i++) { // check divisibility
+            if(n % i == 0) // n has a factor other than 1 and itself → not prime
+                return false;
+        }
+        return true;
+    }
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.print("Enter the starting number: ");
+        int start = scanner.nextInt();
+
+        System.out.print("Enter the ending number: ");
+        int end = scanner.nextInt();
+
+        System.out.println("Prime numbers between " + start + " and " + end + " are:");
+
+        // Loop through the range and print primes.
+        for(int num = start; num <= end; num++) {
+            if(isPrime(num)) {
+                System.out.print(num + " ");
+            }
+        }
+    }
+}