add more

Maths/Factorial.java

@@ -0,0 +1,25 @@
+package Maths;
+
+public class Factorial {
+    public static void main(String[] args) {
+        int n = 5;
+        System.out.println(n + "! = " + factorial(n));
+    }
+
+    /**
+     * Calculate factorial
+     *
+     * @param n the number
+     * @return the factorial of {@code n}
+     */
+    public static long factorial(int n) {
+        if (n < 0) {
+            throw new ArithmeticException("n < 0");
+        }
+        long fac = 1;
+        for (int i = 1; i <= n; ++i) {
+            fac *= i;
+        }
+        return fac;
+    }
+}