feat: Add FactorialProgram with recursive factorial calculation

WHAT the code does:
- Defines a `FactorialProgram` class to compute factorial of a number using recursion.
- `factorial(int n)`:
  - **Base case**: if `n == 1`, prints `"Factorial(1) = 1"` and returns 1.
  - **Recursive case**: prints current formula (`n * Factorial(n-1)`) and recursively calls `factorial(n-1)`.
- `main()` calls `factorial(7)` and prints the result.

WHY this matters:
- Demonstrates **recursion** in Java with factorial, a classic example.
- Shows **base case and recursive case structure**.
- Helps understand how recursive calls expand and collapse during execution.

HOW it works (factorial(7)):
1. Prints: `Factorial(7) = 7 * Factorial(6)`.
2. Calls `factorial(6)` → prints `Factorial(6) = 6 * Factorial(5)`.
3. Continues until `Factorial(1) = 1`.
4. Call stack unwinds, multiplying results → `5040`.

Tips & gotchas:
- Factorial grows very fast — `int` will overflow beyond 12! → use `long` or `BigInteger` for larger inputs.
- No check for `n <= 0` → negative or zero input leads to infinite recursion or incorrect results.
- Printing inside recursion is useful for learning but should be removed in production for efficiency.

Use-cases:
- Educational demo for **recursion basics**.
- Useful in algorithm teaching (factorials, Fibonacci, recursion patterns).
- Foundation for more advanced recursion problems.
- Can be adapted for iterative factorial implementations to compare performance.

Short key: algo-factorial-recursion-trace.

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

Author: Someshdiwan

Section10Methods/RecurssionPractice/src/FactorialProgram.java

@@ -1,27 +1,26 @@
 public class FactorialProgram {
     public static void main(String[] args) {
         System.out.println(factorial(7));
-
-        /*
-        Number Multiply by each Preceding number.
-        5! = 5 * 4 * 3 * 2 * 1 = 120
-
-        if u called method inside itself i will repeat infinite many times.
-        need Base case to know when to stop the method.
-        Base case need.
-        */
-
     }
-    public static int factorial(int n)
-    {
+    public static int factorial(int n) {
         if(n == 1) {
             System.out.println("Factorial("+n+") = 1");
             //Base case is 1. Factorial of 1 is 1.
             return 1;
         }
         else {
-            System.out.println("Factorial(" + n + ") = " + n + " * Factorial(" + (n-1)+ ")"); //Printing current value and Formula version.
-            return n * factorial(n - 1); //current number n and n * ( n - 1);
+            System.out.println("Factorial(" + n + ") = " + n + " * Factorial(" + (n-1)+ ")");
+            /*Printing current value and Formula version.*/
+
+            return n * factorial(n - 1);
+            //current number n.  so, n * ( n - 1);  5 * (5 - 1) = 20.
         }
     }
 }
+
+/* Number Multiply by each Preceding number.
+   5! = 5 * 4 * 3 * 2 * 1 = 120
+   if u called method inside itself i will repeat infinite many times.
+   need Base case to know when to stop the method.
+   Base case need.
+*/