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);
    }

}