Nodes, a NetBeans presentation object

You've already heard the term Node. I've used it several times to describe what and where to click. Officially, a Node represents one element in a hierarchy of objects (beans). It provides all the methods that are needed for communication between an explorer view and the bean. In the explorer section of our application, we want to represent a list of photos to the user. We'll represent each photo, as well as the year and month in which it was taken, as a Node. To display these Nodes, we'll use a NetBeans class called the BeanTreeView, which will display this node hierarchy as a tree. There are a few more concepts to learn, but let's start with what we have first.

We'll begin by defining our Nodes, which will serve as a sort of wrapper or bridge between our application's business domain model and the NetBeans APIs. We have not, of course, defined such a model, so we need to settle on that now. Our basic data item is a photograph, a file on disk that holds...