【第三周】第三章习题3.5

//2016.9.17//马康泰//编写一个应用程序求1!+2!+...+20!。public class Test {  public static void main(String args[]){            int sum=0,fac=0;            int n=1;            Factorial a=new Factorial();            while(n<21){                fac=a.factorial(n);                sum=sum+fac;                n++;            }       System.out.println(sum);        } }public class Factorial {  public int factorial(int i){//阶乘            int j,result=1;            for(j=1;j<=i;j++){                result=result*j;            }          return result;    }  }