public class Librarian {

    private Vector <Book> list;

    public Librarian () {
        list = new Vector<Book>();
    }

    public void add (Book b) {
        list.add(b);
    }

    public void remove (Book b) {
        if (list.contains(b)) {
            list.remove(b);
        } else {
            System.out.println("Book not found!");
        }
    }

    //inner class book
    class Book {
        //add methods and parameters
    }
}