java经典算法_021利用递归方法求5!

package wzs.arithmetics;

import java.util.Scanner;

//  题目：利用递归方法求5!。 
public class Test_wzs21
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        int a = input.nextInt();
        System.out.println(a + "!=" + recurrence(a));
    }

    /**
     * 阶乘
     * @param a 阶乘的数
     * @return
     */
    static int recurrence(int a)
    {
        int sum = 0;
        if (a <= 0)
        {
            System.out.println("请输入正确的数.");
            System.exit(0);
        }
        if (a == 1)
        {
            sum = 1;
        }
        else
        {
            sum = a * recurrence(a - 1);
        }
        return sum;
    }
}