Chapter 11, Problem 3P

One of the most common examples of recursion is an algorithm to calculate the factorial of an integer. The notation n! is used for the factorial of the integer n and is defined as follows:

0! is equal to 1

1! is equal to 1

21 is equal to 2 × 1 = 2

3! is equal to 3 × 2 × 1 = 6

4! is equal to 4 × 3 × 2 × 1 = 24

…

n! is equal to n × (n - 1) × (n- 2) × … × 3 × 2 × 1

An alternative way to describe the calculation of n! is the recursive formula n × (n−1)!, plus a base case of 0!, which is 1. Write a static method that implements this recursive formula for factorials. Place the method in a test program that allows the user to enter values for n until signaling an end to execution.