Resolved: Needs a file header (nowadays LGPL+EPL). See other files for
example.
Fixed: Shouldn't this be DirectedGraph? 
from https://github.com/jgrapht/jgrapht/pull/73/files#r9410194
make class variable DirectedGraph instead of Graph
Fixed comment: Can't this be optimized to only examine the incoming
edges? from https://github.com/jgrapht/jgrapht/pull/73/files