java 利用循环完成阶层运算的例子

import java.math.BigInteger;

public class Test {
public static BigInteger factorial(int num) throws IllegalArgumentException {
if(num < 0) throw new IllegalArgumentException("参数需大于等于0");
if(num == 0) return BigInteger.valueOf(1);
BigInteger result = BigInteger.valueOf(1);
for(int i=1; i<=num; i++) {
result = result.multiply(BigInteger.valueOf(i));
}
return result;
}

public static void main(String[] args) throws Exception {
BigInteger result = BigInteger.valueOf(0);
for(int i=1; i<=15; i++) {
result = result.add(factorial(i));
}

System.out.println(result);
}
}

public class Te{
public static void main(String[] args){
int n=15;
int s=0;
int tep=1;
for(int i=1;i<=n;i++){
tep=1;
for(int j=1;j<=i;j++)
tep*=j;
s+=tep;
}
System.out.println(s);
}