reflection links two domains

class Library {

Hashtable books;

Library() {

books = new Hashtable(100);

}

public Book find(User u, String title) {

if(books.containsKey(title)) {

Book b = (Book)books.get(title);

if (b != null) {

if (b.get_borrower() == null)

b.set_borrower(u);

return b;

}

return null;

}