这是为啥呢?
package zh.codegym.task.task15.task1531;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.BigInteger;
/*
阶乘
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int input = Integer.parseInt(reader.readLine());
reader.close();
System.out.println(factorial(input));
}
public static String factorial(int n) {
//在此编写你的代码
if(n<=0)
return "0! = 1";
BigDecimal lottery=new BigDecimal("1");
//lottery=lottery*(n-i+1)/i
for(int i=1;i<=n;i++){
lottery=lottery.multiply(new BigDecimal(i));
}
return lottery.toString();
}
}