feat: add recursive FactorialCalculator.java for Hacktoberfest

Factorial_Number_Of_N/FactorialCalculator.java

@@ -0,0 +1,29 @@
+import java.util.Scanner;
+
+public class FactorialCalculator {
+
+    public static long findFactorial(int n) {
+        if (n <= 1) {
+            return 1;
+        }
+        return n * findFactorial(n - 1);
+    }
+
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
+
+        System.out.println("FACTORIAL FINDER");
+        System.out.print("Enter a number: ");
+
+        int num = input.nextInt();
+
+        if (num < 0) {
+            System.out.println("Cannot find factorial of negative number!");
+        } else {
+            long answer = findFactorial(num);
+            System.out.println(num + "! = " + answer);
+        }
+
+        input.close();
+    }
+}