Java开发练习1，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);

}

}