* factorial using using iteration

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

Maths/Ceil.java

@@ -0,0 +1,32 @@
+package Maths;
+
+public class Ceil {
+    public static void main(String[] args) {
+        assert ceil(10) == Math.ceil(10);
+        assert ceil(-10) == Math.ceil(-10);
+        assert ceil(10.0) == Math.ceil(10.0);
+        assert ceil(-10.0) == Math.ceil(-10.0);
+        assert ceil(10.1) == Math.ceil(10.1);
+        assert ceil(-10.1) == Math.ceil(-10.1);
+        assert ceil(0) == Math.ceil(0);
+        assert ceil(-0) == Math.ceil(-0);
+        assert ceil(0.0) == Math.ceil(0.0);
+        assert ceil(-0.0) == Math.ceil(-0.0);
+    }
+
+    /**
+     * Returns the smallest (closest to negative infinity)
+     *
+     * @param number the number
+     * @return the smallest (closest to negative infinity) of given {@code number}
+     */
+    public static double ceil(double number) {
+        if (number - (int) number == 0) {
+            return number;
+        } else if (number - (int) number > 0) {
+            return (int) (number + 1);
+        } else {
+            return (int) number;
+        }
+    }
+}