How Can I Do Library Management In Java (the Code)?

I am working in a project to manage the books in a library. In the project there is to types of users so when you do the login through a GUI you must be able to identify the type of User to display the appropriate screen that they are allowed to work with and I also have to text files, one for one type of user which is the administrator and the other that is a student.  Most of the project works but my only concern is that I do not know how to link my login class with the user file that will be loading the books into my library class. How can  I create an object that contains all information of user, so lthat my library class can tell which user to display and in this way display just the books that this user has.