feat: Add Questions class with prime check and Armstrong number listing

WHAT the code does:
- Defines a `Questions` class for practicing number-related problems.
- Prompts user for input and checks if the number is prime (`isPrime()`).
- Prints all 3-digit Armstrong numbers (100–999) using `isArmstrong()`.

WHY this matters:
- Demonstrates **user input handling** with `Scanner`.
- Shows **prime number check** using efficient loop up to √n.
- Implements **Armstrong number check** for 3-digit numbers.
- Useful educational example combining loops, conditionals, and modular arithmetic.

HOW it works:
1. `isPrime(int n)`:
   - Returns false if `n <= 1`.
   - Loops from `2` to `√n`.
   - If divisor found, returns false; otherwise true.
2. `isArmstrong(int n)`:
   - Extracts digits of `n`.
   - Cubes each digit and sums them.
   - Returns true if sum equals original number.
3. `main()`:
   - Takes a number from user input and prints prime status.
   - Iterates from 100–999 and prints Armstrong numbers.

Tips & gotchas:
- `Scanner` should be closed after use to prevent resource leaks (`in.close()`).
- Prime check optimized with `c * c <= n` → faster than looping to `n/2`.
- `isArmstrong()` works only for 3-digit numbers; for n-digit, use `(int)Math.pow(rem, digits)`.
- Input validation for non-integer entries not handled (will throw exception).

Use-cases:
- Competitive programming or coding interviews.
- Teaching examples for **loops, conditionals, math operations**.
- Can be extended to find primes/Armstrong numbers in any range.
- Base utility for number theory problems.

Short key: algo-prime-armstrong-check.

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

Author: Someshdiwan

Section10Methods/Methods 2.O/src/Questions.java

@@ -3,10 +3,13 @@
 public class Questions {
     public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
-//        int n = in.nextInt();
-//        boolean ans = isPrime(n);
-//        System.out.println(ans);
+        System.out.println("Enter a number to check it is prime or not: ");
 
+        int n = in.nextInt();
+        boolean ans = isPrime(n);
+        System.out.println(ans);
+
+        System.out.println("List of Armstrong numbers in range 100 to 1000 are: ");
         for (int i = 100; i < 1000; i++) {
             if (isArmstrong(i)) {
                 System.out.print(i + " ");
@@ -24,10 +27,10 @@ static boolean isArmstrong(int n) {
             n = n / 10;
             sum = sum + rem*rem*rem;
         }
-
         return sum == original;
     }
 
+    //declaring a method 'isPrime' and calling this method in main method.
     static boolean isPrime(int n) {
         if (n <= 1) {
             return false;