An implementation of GraphGenerator used to generate an optimized graph
representing a line network. Graphs are generated by supplying the generator
with objects of type LineSegment via the add(Object) method.
For each line segment added, an edge in the graph is created. The builder
records the end coordinates of each line added, and maintains a map of
coordinates to nodes, creating nodes when neccessary.
Edges created by the generator are of type OptBasicEdge.
Nodes created by the generator are of type OptXYNode.
Since building optimized graphs requires knowing the degree of nodes before
creating them, the physical construction of the graph is delayed until a call
to generate() is made. No component is created with a call to add(Object),
only information about the object is recorded.
Justin Deoliveira, Refractions Research Inc, email@example.com
Returns the edge which represents a line. This method must be called
after the call to generate(). Note that if the exact same line
has been added to the graph multiple times, then only one of the edges
that represents it will be returned. It is undefined which edge will be