queue.add(_startNode);
_predecessor[graph.nodeLabel(_startNode)] = -1;
while (!queue.isEmpty()) {
Node u = (Node) queue.get(0);
Collection successors = graph.successors(u);
if (successors != null) {
for (Iterator successorNodes = successors.iterator(); successorNodes
.hasNext();) {
Node v = (Node) successorNodes.next();