Java How to Program (early objects), 9/e

18.3 Example Using Recursion: Factorials

Let’s write a recursive program to perform a popular mathematical calculation. Consider the factorial of a positive integer n, written n! (pronounced “n factorial”), which is the product

n · (n – 1) · (n – 2) · … · 1

with 1! equal to 1 and 0! defined to be 1. For example, 5! is the product 5 · 4 · 3 · 2 · 1, which is equal to 120.

The factorial of integer number (where number ≥ 0) can be calculated iteratively (non-recursively) using a for statement as follows:

A recursive declaration of the factorial ...