Judge whether the date time exceeds 31 days

At the end of the project , It is necessary to judge whether students are overdue , exceed 31 Days are overdue , So the following method is used .

/** *  Enter two times , One is the start time , The other is the end time  *  Compare the two , Judge whether it is more than 31 God  * @param startTime * @param endTime * @return */
	public boolean checkOverdue(String startTime ,String endTime){
    
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		try {
    
			Date end = sdf.parse(endTime);
			Date start = sdf.parse(startTime);
			long day = 60*1000*60*24; // 1 God 
			if(end.getTime()-(day*31) > start.getTime()){
    
				return true;
			}else{
    
				return false;
			}
		} catch (ParseException e) {
    
			e.printStackTrace();
		}
		return false;
	}

Count the overdue times , First, check the borrowing records （ Here is the specific implementation of business functions ）

/** *  according to sid Find out the student's borrowing record  *  Then judge the overdue according to the borrowing time and return time in the borrowing record  *  Overdue is divided into the following three situations  * 1.  Never borrowed a book , Not overdue  * 2.  Borrowed books but not returned  *  Take out the borrowing time , Then take out the current time , If not more than 31 God , Is not overdue  *  Take out the borrowing time , Then take out the current time , If exceeded 31 God , Then overdue  * 3.  Borrowed books and returned them  *  Calculate the borrowing time directly , If exceeded 31 God , Then overdue  * @param sid * @return */
	public String checkOverdueBySid(int sid){
    
		int num=0;
		// Here is to check the borrowing record first 
		List<Borrow> borrows = borrowMapper.queryBorrowBySid(sid);
		if(borrows==null) {
    
			return " No overdue records ";
		}else{
    
			for (Borrow borrow : borrows) {
    
				if("".equals(borrow.getReturnTime())||borrow.getReturnTime()==null){
    
					Date date = new Date();
					SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
					String nowTime = sdf.format(date);
					if(checkOverdue(borrow.getBorrowTime(),nowTime)){
    
						num+=1;
					}
				}else{
    
					if(checkOverdue(borrow.getBorrowTime(),borrow.getReturnTime())){
    
						num+=1;
					}
				}
			}
			if(num==0){
    
				return " No overdue records ";
			}else{
    
				return " Within the time limit "+num+" Time ";
			}
		}

	}