SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date endTimeString = null;
Date nowtimeString = new Date(); //当前时间
long days = 0;
try {
endTimeString = sdf.parse(peTrainingClass.getEndDate().toString()); //某个时间
long endTime = endTimeString.getTime();
long now = nowtimeString.getTime();
Calendar calen = Calendar.getInstance();
long diff = now - endTime ;
days = diff / (1000 * 60 * 60 * 24);//转换为天数;
System.out.println(days);
//此处根据days对应的天数来处理对应的业务;
} catch (ParseException e) {
e.printStackTrace();
}