How to initialize the constructor

Question

Public class Library{
private Catalogue catalogue;
private LinkedList<Patron> patrons;

public library(){
//what code to initialise
}
}

And another CLASS

public class Catalogue{
private Library library;
private LinkedList<Book> books;

public catalogue( Library library){
//what code to initialize

}
}

Answer 1

public class Library{
private Catalogue catalogue;
private LinkedList<Patron> patrons;

public Library(){
//code to initialise
patrons = new LinkedList();
catalogue = new Catalogue(this);
}
}

And another CLASS

public class Catalogue{
private Library library;
private LinkedList<Book> books;

public Catalogue(Library library){
//code to initialize
this.library = library;
books = new LinkedList();
}
}