Hi all, I am learning java. I am trying to use composite design pattern. I am trying to use following logic. ( Don't laugh I know it is very basic :) )

Item -> interface
Folder -> class
File -> class

In folder class, can I create an arraylist of Item to store files information?

ArrayList<Item> info = ArrayList<Item>();

Or should I use Folder Arraylist?

ArrayList<Folder> info = ArrayList<Folder>();

I don't know if interface can store real data as there is no variable just function definitions.

Thanks for helping a newbie :)