Add recursive implementation of Factorial with user input

Author: konduri-lakshmi-prasanna

src/main/java/com/thealgorithms/recursion/Factorial.java

@@ -0,0 +1,44 @@
+package com.thealgorithms.recursion;
+
+import java.util.Scanner;
+
+/**
+ * This class provides a recursive implementation of the factorial function.
+ * The factorial of a number n is defined as n! = n × (n-1) × (n-2) × ... × 1
+ * with the base case 0! = 1.
+ */
+public class Factorial {
+
+    /**
+     * Recursive method to calculate factorial.
+     *
+     * @param n the number to find factorial of
+     * @return factorial of n
+     * @throws IllegalArgumentException if n is negative
+     */
+    public static long factorial(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Number must be non-negative");
+        }
+        if (n == 0 || n == 1) {
+            return 1;
+        }
+        return n * factorial(n - 1);
+    }
+
+    // Main method with user input
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter a number to find its factorial: ");
+
+        int num = scanner.nextInt();
+        scanner.close();
+
+        try {
+            long result = factorial(num);
+            System.out.println("Factorial of " + num + " is: " + result);
+        } catch (IllegalArgumentException e) {
+            System.out.println(e.getMessage());
+        }
+    }
+}