目录

程序清单18_1ComputeFactorial.java

程序清单18_2ComputeFibonacci.java

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程序清单18_1ComputeFactorial.java

package chapter_18;import java.util.Scanner;public class 程序清单18_1ComputeFactorial {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a nonnegative integer:");int n = input.nextInt();System.out.println("Factorial of " + n + " is " + factorial(n));}public static long factorial(int n) {if(n == 0)return 1;else return n * factorial(n - 1);}
}

输出结果

Enter a nonnegative integer:4
Factorial of 4 is 24

程序清单18_2ComputeFibonacci.java

package chapter_18;import java.util.Scanner;public class 程序清单18_2ComputeFibonacci {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter an index for a Fibonacci number:");int index = input.nextInt();System.out.println("The Fibonacci number at index "+ index+" is " + fib(index));}public static long fib(long index) {if (index == 0) return 0;else if(index == 1)return 1;else return fib(index - 1) + fib(index - 2);}
}

 输出结果

Enter an index for a Fibonacci number:7
The Fibonacci number at index 7 is 13