Which would be the better approach?

Question

Hello!
I'm a working java professional, but has taken on some courses on the local University.
Of course there is a difference in how things are solved in theory and practise, but it makes
me wonder what the "best" solutions to some problems are...
Consider the following structure:
class Book{
   private List chapters;
class Chapter{
   private List pages;
   private Book book;
   public Book getBook(){
      return this.book;
class Page{
   private List chars;
   private Chapter chapter;
   public Chapter getChapter(){
      return this.chapter;
class Char{
   private Page page;
   public Page getPage(){
      return this.page;
   public void method(){
      // blabla
}Check out the "method" in class Char. Say I would like to have a reference to the Book that this character is in. I would say that I have two choices:
1. call getPage().getChapter().getBook()
2. put a getBook() in each of the classes
Where I come from it is a bad thing to "expose structure", the first example exposes structure.
But, it is also a bad thing to let classes do things that they aren't responsible for (cohesion).
What solution would you prefer?

Answer 1

Hi!
With getPage().getChapter().getBook() surely you are having too high coupling and also exposure.
In just one code line you are coupling to three classes and also violating twice De Meter assumption about not accessing class internal structures as character accesses to chapter through Page and to Book through Chapter.
The problem is in the main design idea i think...you are just designing data structures as if you would be designing db entities, with double dispatches between all classes as you would connect db tables with joins but this ends with no real reusability, think to this.... you can't reuse any of your classes without carrying all of the others.
For example why a character should be linked to a book, a character can be an actor of many books but it's not connected to a specific book. A character class should be reusable in movies, lyrichs, books, dreams. Why you want a Chapter to know what is a book?? In concrete that means that every time you modify the book class you must recompile also the chapter cause it's directly connected to the book class and also you can use your Chapter class only within your Book class, it's not reusable at all.
You want to search characters within books? ok you just need an external components that will enter the library and ask to any book what's it about and which characters play in it if it is a characters book,
so everyone will just expose services for the data it's responsible for.