/**
* Topological sorts the graph using and returns the order as list. It tries to bring Objects on
* one common level in a sorted order. If a loop is detected, it returns null as no sorting is
* possible.
*
* @return DOCUMENT ME!
* @throws IllegalStateException DOCUMENT ME!
*/
public final Set<T> orderedTopologicalSort() {
final Set<T> result = TypeSafeCollections.newLinkedHashSet();
final Map<T, Set<T>> orderedAdjacencyListCopy = TypeSafeCollections.newLinkedHashMap();
final List<T> pathsToOrderList = TypeSafeCollections.newArrayList(adjacencyList.keySet());
if (comparator != null) {
Collections.sort(pathsToOrderList, comparator);
}
for (final T item : pathsToOrderList) {
orderedAdjacencyListCopy.put(item, new HashSet<T>(adjacencyList.get(item)));
}
while (!orderedAdjacencyListCopy.isEmpty()) {
final List<T> current = TypeSafeCollections.newArrayList();
final Iterator<Entry<T, Set<T>>> it = orderedAdjacencyListCopy.entrySet().iterator();
T item = null;
while (it.hasNext()) {
final Entry<T, Set<T>> entry = it.next();
item = entry.getKey();
final Set<T> chk = entry.getValue();
if ((chk == null) || chk.isEmpty()) {
it.remove();
current.add(item);
for (final Set<T> set : orderedAdjacencyListCopy.values()) {
set.remove(item);
}
}
}
if (current.isEmpty()) {
throw new IllegalStateException(
"Relationgraph has cyclic dependencies on item " + item + "!");
}
result.addAll(current);
}
return result;
}
/**
* DOCUMENT ME!
*
* @return DOCUMENT ME!
*/
public final Set<T> reverseOrderedTopologicalSort() {
final List<T> tmp = TypeSafeCollections.newArrayList(orderedTopologicalSort());
Collections.reverse(tmp);
final Set<T> res = TypeSafeCollections.newLinkedHashSet(tmp);
return res;
}
