java經典演算法_021利用遞迴方法求5!

package wzs.arithmetics;import java.util.Scanner;//  題目：利用遞迴方法求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));    }    /**     * 階乘     * @param a 階乘的數     * @return     */    static int recurrence(int a)    {        int sum = 0;        if (a <= 0)        {            System.out.println("請輸入正確的數.");            System.exit(0);        }        if (a == 1)        {            sum = 1;        }        else        {            sum = a * recurrence(a - 1);        }        return sum;    }}