处理金额都用这个数据类型，不用Int
判断BigDecimal 类型是否为0，应该用如下方法：
vvv.compareTo(BigDecimal.ZERO) == 0
除法运算的取整方法：
https://blog.csdn.net/bailu666666/article/details/79829902?utm_medium=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-1.control&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7EBlogCommendFromMachineLearnPai2%7Edefault-1.control
BigDecimal的常用方法：https://www.cnblogs.com/zhangyinhua/p/11545305.html#:~:text=Java%E5%9C%A8java.math%E5%8C%85%E4%B8%AD%E6%8F%90%E4%BE%9B%E7%9A%84API%E7%B1%BBBigDecimal%EF%BC%8C%E7%94%A8%E6%9D%A5%E5%AF%B9%E8%B6%85%E8%BF%8716%E4%BD%8D%E6%9C%89%E6%95%88%E4%BD%8D%E7%9A%84%E6%95%B0%E8%BF%9B%E8%A1%8C%E7%B2%BE%E7%A1%AE%E7%9A%84%E8%BF%90%E7%AE%97%E3%80%82,%E5%8F%8C%E7%B2%BE%E5%BA%A6%E6%B5%AE%E7%82%B9%E5%9E%8B%E5%8F%98%E9%87%8Fdouble%E5%8F%AF%E4%BB%A5%E5%A4%84%E7%90%8616%E4%BD%8D%E6%9C%89%E6%95%88%E6%95%B0%EF%BC%8C%E4%BD%86%E5%9C%A8%E5%AE%9E%E9%99%85%E5%BA%94%E7%94%A8%E4%B8%AD%EF%BC%8C%E5%8F%AF%E8%83%BD%E9%9C%80%E8%A6%81%E5%AF%B9%E6%9B%B4%E5%A4%A7%E6%88%96%E8%80%85%E6%9B%B4%E5%B0%8F%E7%9A%84%E6%95%B0%E8%BF%9B%E8%A1%8C%E8%BF%90%E7%AE%97%E5%92%8C%E5%A4%84%E7%90%86%E3%80%82