It is interesting to watch recursion in action. Modify the factorial method in Fig. 18.3 to print its local variable and recursive-call parameter.

For each recursive call, display the outputs on a separate line and add a level of indentation. Do your utmost to make the outputs clear, interesting, and meaningful. Your goal here is to design and implement an output format that makes it easier to understand recursion.

// Fig. 18.3: FactorialCalculator.java // Recursive factorial method. public class FactorialCalculator { // recursive method factorial (assumes its parameter is >= 0 public static long factorial(long number) { if (number <= 1) // test for base case return 1; // base cases: 0! = 1 and 1! = 1 else // recursion step return number * factorial(number - 1); } // output factorials for values 0-21 public static void main(String[] args) { // calculate the factorials of 0 through 21 for (int counter = 0; counter <= 21; counter++) System.out.printf("%d! = %d%n", counter, factorial(counter)); } } // end class FactorialCalculator