Java开发练习1，求1+2!+3!+...+20!的和

求1+2!+3!+...+20!的和

public class Jiecheng {  
  
    public static void main(String[] args) {  
        // TODO Auto-generated method stub  
            double i,m,sum1 = 1;  
            double sum2=0;  
  
        for(i=1;i<=20;i++)  
        {  
            m=i;      
            sum1=m*sum1;  
            sum2+=sum1;  
        }  
        System.out.printf("%18.0f",sum2);  
  
    }  
  
}