/**
* Sets an ordering between two nodes. When an iterator is requested, the first node will appear
* earlier in the sequence than the second node. If a prior ordering existed between the nodes in
* the opposite order, it is removed.
*
* @return <code>true</code> if no prior ordering existed between the nodes, <code>false</code>
* otherwise.
*/
public boolean setOrdering(Object first, Object second) {
DigraphNode firstPONode = (DigraphNode) poNodes.get(first);
DigraphNode secondPONode = (DigraphNode) poNodes.get(second);
secondPONode.removeEdge(secondPONode);
return firstPONode.addEdge(secondPONode);
}
/** Removes an <code>Object</code> from this <code>PartiallyOrderedSet</code>. */
public boolean remove(Object o) {
DigraphNode node = (DigraphNode) poNodes.get(o);
if (node == null) {
return false;
}
poNodes.remove(o);
node.dispose();
return true;
}
public PartialOrderIterator(Iterator iter) {
// Initialize scratch in-degree values, zero list
while (iter.hasNext()) {
DigraphNode node = (DigraphNode) iter.next();
int inDegree = node.getInDegree();
inDegrees.put(node, new Integer(inDegree));
// Add nodes with zero in-degree to the zero list
if (inDegree == 0) {
zeroList.add(node);
}
}
}
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();
}
/** Returns <code>true</code> if an ordering exists between two nodes. */
public boolean hasOrdering(Object preferred, Object other) {
DigraphNode preferredPONode = (DigraphNode) poNodes.get(preferred);
DigraphNode otherPONode = (DigraphNode) poNodes.get(other);
return preferredPONode.hasEdge(otherPONode);
}
