Unit 10: Recursion

public static int factorial(int n) {
    if (n == 0) {          // base case
        return 1;
    }
    return n * factorial(n - 1);  // recursive case
}

factorial(4)
= 4 * factorial(3)
= 4 * 3 * factorial(2)
= 4 * 3 * 2 * factorial(1)
= 4 * 3 * 2 * 1 * factorial(0)
= 4 * 3 * 2 * 1 * 1
= 24