- Added returnBook(User, Book) which will update both the users and the
books upon success on returning the book
- Added currentDay() that would return the current date in int array
- Added calDueDate(int) that takes the current date from currentDay()
and calculate the due date from there

Main.java
- removed redundant newBook()

Book.java
- Added a condition if the book is not overdue

BookFactory.java
- Removed empty newBook()
- Added “throw new NullPointerException()” on both getBook() if Book is
not found

Book.java
- Added comments for Book.java
- Added getter for id
- Added setter for title
- Removed the need of ‘status’ in constructor
- overdueFine(int[]) not commented as it needs to be updated

BookFactory.java
- need for (String status) is removed

Book.java
- Added String type ‘title’
- Added new constructor to include ’title’

Main.java
- Added Main.java (mostly still empty)

BookFactory.java
- Added newBook(String) for the new ‘title’ implementation
- Added getBook(String) to look through ArrayList for Book with the
given ‘title’
- Error handling for both getBook still needs more work