SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd");
Date date1 = (Date) sd.parse(cstartdate);
Date date2 = (Date) sd.parse(validDate);
int days = (int) ((date1.getTime() - date2.getTime()) / (1000*3600*24));
String 类型的日期格式为 "yyyy-MM-dd"
转自:
https://blog.csdn.net/weixin_42030389/article/details/82965710