Graph is part of a framework. It supplies nearly all of the methods to support a generic graph editor.
SimpleGraph is a client-defined extension that supplies the geometric shapes of the nodes and edges to be used in the graph.
Graph is an abstract class. It needs a constructor to initialize the variables to do its work.
(From Cay Horstmann�s Object Oriented Design &
Patterns)
[ May 27, 2003: Message edited by: Marlene Miller ]