The Explorer is really an abstraction that needs a
view
to actually display the nodes.
The same nodes might be represented as an expandable tree, as a tabbed
pane showing icons, as a popup menu, etc. The
Explorer API
permits creation of new views, and contains several standard views
that may be reused in special contexts.
This class provide access to thread safe layer that
reflects the hierarchy of Nodes, but is updated only in
event dispatch thread (in contrast to nodes that can be updated from any thread).
That is why this class is useful for writers of explorer views,
because it guarantees that all changes will be done safely.