Write a method that calculates the factorial of a given number.

Factorial is the product of all positive integers less than or equal to n. For example, factorial(4) = 4x3x2x1 = 24.

TIP: To make it more interesting, try to do it recursively.

Factorial is the product of all positive integers less than or equal to n. For example, factorial(4) = 4x3x2x1 = 24.

TIP: To make it more interesting, try to do it recursively.

public Integer factorial(Integer n) {

}