public void addEdge(Course source, Course target) {
if (this.edges.containsKey(source.getName())) {
this.edges.get(source.getName()).put(target.getName(), target);
} else {
this.edges.put(source.getName(), new HashMap<String, Course>());
this.edges.get(source.getName()).put(target.getName(), target);
}
}
public void addNode(Course course) {
if (!this.nodes.containsKey(course.getName())) {
this.nodes.put(course.getName(), course);
}
}