MGraph resultGraph = new SimpleMGraph();
Iterator<NonLiteral> users = userManager.getUsers();
SortedSet<GraphNode> sortedSet = new TreeSet<GraphNode>(
new UserComparator());
Lock readLock = systemGraph.getLock().readLock();
readLock.lock();
try {
while (users.hasNext()) {
sortedSet.add(new GraphNode(users.next(), systemGraph));