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From: Joris K. <de...@gm...> - 2015-02-26 15:30:11
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Without seeing more code it's difficult to check what goes wrong. It's very
unlikely that there is a problem in the AbstractBaseGraph implementation.
Check your implementation of your getSlave method first.
Why don't you use the following:
public int nbrDescendants(Site s){
int i=0;
Set<Lien> children = graph.incomingEdgesOf(s);
for(Lien lien: children){
i+=graph.inDegreeOf(graph.getEdgeTarget(lien));
}
return i;
}
Btw, I don't really see the point of this code. If there are 5 incoming
edges for a given site s, then this method will return 5*5=25? Unless I
misunderstood what you mean with "destination vertex of an edge"?
best,
Joris
On Thu, Feb 26, 2015 at 3:39 PM, mokhtar aitbaomar <
ait...@gm...> wrote:
> Hello everyone;
> I have a project in which i need to implement a graph (directed &
> weighted), and i found your work which helped me a lot, but i have a
> problem and i want you to help me out.
> When i create my SimpleDirectedWeightedGraph object "graph" and insret the
> vertexes (type Site in my case) and edges (Type Lien in my case) and apply
> the "incomingEdgesOf(Vertex v)" method to the "graph", i put the result in
> a Set<Lien> and i find that the size (number of incoming edges) is correct
> but when i apply the method again on the resulting set of edges "so that i
> can calculate the number of descendants of an Edge" an exception in thrown
> which says java.lang.NullPointerException .
>
> -------------------------------------------------------------------------------
> Here is my code:
> //CALCULATE THE NUMBER OF DESCENDANTS OF AN EDGE (WHERE SITE S IS THE
> DESTINATION VERTEX) IN THE GRAPH
> public int nbrDescendants(Site s)
> {
> int i=0;
> Set<Lien> children = graph.incomingEdgesOf(s);
> Iterator<Lien> it = children.iterator();
> while(it.hasNext())
> {
> i+= graph.incomingEdgesOf(it.next().getSlave()).size();
> //getSlave() returs in my case the destination vertex of the edge
> }
> i+=children.size();
> return i;
> }
>
> -----------------------------------------------------------------------------------
> Here is the error message:
> java.lang.NullPointerException
> at
> org.jgrapht.graph.AbstractGraph.assertVertexExist(AbstractGraph.java:156)
> at
> org.jgrapht.graph.AbstractBaseGraph$DirectedSpecifics.getEdgeContainer(AbstractBaseGraph.java:925)
> at
> org.jgrapht.graph.AbstractBaseGraph$DirectedSpecifics.incomingEdgesOf(AbstractBaseGraph.java:885)
> at
> org.jgrapht.graph.AbstractBaseGraph.incomingEdgesOf(AbstractBaseGraph.java:411)
> at inwi.capacite.calcul.Reseau.nbrDescendants(Reseau.java:62)
> at inwi.capacite.calcul.Rapport.main(Rapport.java:86)
>
> ------------------------------------------------------------------------------------
> And finally i'm not sure but i think that the error comes from the
> AbstractBaseGraph.java file, where i found this:
>
> */
> public Set<EE> getUnmodifiableOutgoingEdges()
> {
> if (unmodifiableOutgoing == null) {
> unmodifiableOutgoing =
> Collections.unmodifiableSet(outgoing);
> }
>
> return unmodifiableOutgoing;
> }
>
> i think this methode must return Set<E> and not Set<EE>.
>
>
>
>
> ------------------------------------------------------------------------------
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