public Object next() {
DigraphNode first = (DigraphNode) zeroList.removeFirst();
// For each out node of the output node, decrement its in-degree
Iterator outNodes = first.getOutNodes();
while (outNodes.hasNext()) {
DigraphNode node = (DigraphNode) outNodes.next();
int inDegree = ((Integer) inDegrees.get(node)).intValue() - 1;
inDegrees.put(node, new Integer(inDegree));
// If the in-degree has fallen to 0, place the node on the list
if (inDegree == 0) {
zeroList.add(node);
}
}
return first.getData();
}
