Re: [jgrapht-users] Documentation, implementation or me?

[John S. <js...@gm...>]

Hi Jonathan,

s2 is a mutable object, and you changed it after adding it to the
graph.  That's why you got unexpected results.

See the section "Good keys" in this article:

http://www.ibm.com/developerworks/java/library/j-jtp02183.html

JVS

On Mon, Nov 15, 2010 at 5:23 PM, Jonathan Cederberg
<jon...@it...> wrote:
> I am a huge fan of jgrapht. However, I have come across a problem with it.
> My understanding is that that the code below should work, but it doesn't. I
> have not dug into the source, but I can imagine that there is a hashcode
> issue, as it no longer seem to find the vertex that is there.
> I am not sure if I have read the docs wrong, programmed wrong, or if this is
> simply a bug. The latter seems unlikely though, since it is such a core
> feature that this type of problem should have been caught long ago.
> Thanks in advance for any help!
> /Jonathan
>
> import java.util.LinkedHashSet;
> import java.util.Set;
> import org.jgrapht.graph.DefaultEdge;
> import org.jgrapht.graph.SimpleGraph;
> public class Main {
> /**
> * @param args
> */
> public static void main(String[] args) {
> SimpleGraph<Set<String>, DefaultEdge> sg =
> new SimpleGraph<Set<String>, DefaultEdge>(DefaultEdge.class);
>
> Set<String> s1, s2;
> s2 = new LinkedHashSet<String>();
> s2.add("y");
> s2.add("z");
>
> sg.addVertex(s2);
>
> s2.remove("z");
>
> // this is true, as expected
> assert(sg.vertexSet().size()==1) : "There is no vertex any more.";
> assert(sg.vertexSet().iterator().next()==s2) : "Not the same vertex!";
>
> // but this is false!
> assert(sg.containsVertex(s2)) : "The vertex is gone!";
> }
> }
>
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