i fixed it, I was doing this:
DefaultDirectedGraph g_graph = new DefaultDirectedGraph();
in the constructor which was creating a new object rather than
instantiating the class member.
thanks
-balaji
On Tue, 8 Mar 2005 09:33:04 -0500, Balaji Iyengar <bri...@gm...> wrote:
> I was just typing some sort of a psuedo code. I got those right in my
> program. It looks like the reference returned by the
> DefaultDirectedGraph constructor is alive only in the body of the
> method it is in. So if you have this:
>
> protected final void sample_method(){
> DefaultDirectedGraph g_graph = new DefaultDirectedGraph();
> Integer tp_obj = new Integer(2);
> g_graph.addVertex(tp_obj);
> }
>
> then it works fine without a nullpointer exception.
>
> thanks
> -balaji
>
> On Tue, 8 Mar 2005 09:07:35 -0500, Bergeron Guyard, Alexandre
> <Ale...@dr...> wrote:
> > Well,
> >
> > From the little I see, I have a few ideas:
> >
> > 1) In your class you declare a method addNode(), but you later call
> > addVertex()....
> >
> > 2) You instanciate a SampleGraph under the name tmp-graph-obj, but use the
> > name tmp-obj to call the addNode()/addVertex() method later on...
> >
> > Hope this helps.
> >
> > Alex
> >
> > -----Original Message-----
> > From: Balaji Iyengar [mailto:bri...@gm...]
> > Sent: March 8, 2005 8:19 AM
> > To: jgr...@li...
> > Subject: [jgrapht-users] graph object instantiation.
> >
> > Hello,
> >
> > I have a DefaultDirectedGraph object as a private member of a class,
> > which i instantiate in the constructor of the class. I then use call
> > the addVertex function later from other files in my code structure.
> > This is how my class looks like:
> >
> > class SampleGraph {
> > private DefaultDirectedGraph g_graph;
> > // other members
> >
> > // constructor
> > SampleGraph(){
> > DefaultDirectedGraph g_graph = new DefaultDirectedGraph();
> > }
> >
> > // wrapper method
> > protected final boolean addNode(Object gnode){
> > return g_graph.addVertex(gnode);
> > }
> > }
> >
> > elsewhere in the code i do:
> >
> > SampleGraph tmp-graph-obj = new SampleGraph ();
> > tmp-obj.addVertex(tmp-node);
> >
> > which should add the tmp-node to the g_graph member of tmp-graph-obj,
> > is this the right way of doing this. I get a null pointer exception
> > here and i cant figure what i am doing wrong here.
> > Any help would be very much appreciated.
> >
> > thanks
> >
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