* factorial using using iteration

* add ceil() to maths
* add combinations() to maths
* add floor() to maths

Maths/Factorial.java

@@ -1,34 +1,27 @@
 package Maths;
-import java.util.*; //for importing scanner
 
 public class Factorial {
-    public static void main(String[] args) { //main method
-           int n = 1;
-           Scanner sc= new Scanner(System.in);
-           System.out.println("Enter Number");
-           n=sc.nextInt();
-           System.out.println(n + "! = " + factorial(n));
+
+    /* Driver Code */
+    public static void main(String[] args) {
+        assert factorial(0) == 1;
+        assert factorial(1) == 1;
+        assert factorial(5) == 120;
+        assert factorial(10) == 3628800;
     }
 
-    //Factorial = n! = n1 * (n-1) * (n-2)*...1
-
     /**
-     * Calculate factorial N
+     * Calculate factorial N using iteration
      *
      * @param n the number
      * @return the factorial of {@code n}
      */
     public static long factorial(int n) {
-        // Using recursion
-        try {
-        	if (n == 0) {
-				return 1; // if n = 0, return factorial of n;
-			}else {
-				return n*factorial(n-1); // While N is greater than 0, call the function again, passing n-1 (Principle of factoring);
-			}
-        }catch (ArithmeticException e) {
-			System.out.println("Dont work with less than 0");
-		}
-		return n;
+        if (n < 0) {
+            throw new IllegalArgumentException("number is negative");
+        }
+        long factorial = 1;
+        for (int i = 1; i <= n; factorial *= i, ++i) ;
+        return factorial;
     }
 }