阶乘的计算方法，范围1-10000

package com.gtja.gmall.eplusmall.entity;

import java.math.BigDecimal;
import java.util.Scanner;

/**
 * Created by CP_wangchao on 2017/6/21.
 */
public class Test {
    public static void main(String arg[]){
        Scanner scanner = new Scanner(System.in);
        int index = scanner.nextInt();
        System.out.print(fun(index));
    }

    public static BigDecimal fun(long index){

        BigDecimal sum = new BigDecimal("1");
        for(int i=1;i<=index;i++){
            sum = sum.multiply(new BigDecimal(String.valueOf(i)));
        }
        return sum;
    }
}