阶乘代码

public class jiecheng2 {

    public static void main(String[] args) {
        // 1+1/2!+1/3!+1/4!=1/5!+...+1/20!=?
        int x=20;

        double a =1;

        for(int z=1;z<=x;z++){
            long y=1;

            for(int i=1;i<=z;i++){

                y=y*i;

            }

                 a=a+(double)(1/(double)y);

        }

        System.out.println(a);
    }

}