Re: [Jung-support] java.lang.NullPointerException from g.findEdge

[Joshua O'M. <jos...@gm...>]

Actually, it does explain it.  There are lots of articles on what happens
if equals() and hashCode() are not consistent; please go take a look.


On Wed, Sep 25, 2013 at 6:14 AM, Han Qi <shm...@gm...> wrote:

> HI Tom, you are right about equals and hashcode.
> But that still does not explain why g.findedge() throw Nullpoiner
> execption and for edge in g.getIncidentEdges(v),  g.edges.get(edge) returns
> null.
> And why change the type of Graph make it ok.
>
> Best
> Qi
>
>
> On Wed, Sep 25, 2013 at 2:57 PM, Tom Nelson <tho...@gm...>wrote:
>
>> My guess is that your Tweet class does not override equals and hashcode,
>> so the new ones you create are never 'equal' to the ones in your graph. You
>> would have the same error with any Java collection, not just the Jung
>> graphs.
>>
>> Tom Nelson
>>
>>
>> On Wed, Sep 25, 2013 at 8:41 AM, Han Qi <shm...@gm...> wrote:
>>
>>> Hi, Joshua,
>>>
>>> thanks for the quick reply.  What I mean ist that:
>>>
>>>  I find sometimes  g.findEdge throw java.lang.
>>> NullPointerException.  With
>>> I then look at the source code of findEdge, it seems thatI that for some
>>> edges it  get from  g.getIncidentEdges(v),  edges.get(edge) returns null.
>>> And this happens when the graph type is UndirectedSparseMultigraph, if I
>>> change it to UndirectedSparseGraph everything goes fine but the programm
>>> becomes much slower.
>>>
>>> Here is the code I use: the graph is pretty big 512,262 notes.
>>>
>>>         Graph<String, List<Tweet[]>> g = new
>>> UndirectedSparseMultigraph<String, List<Tweet[]>>();
>>>
>>>         // add vertexes
>>>         Set<String> UIDs = twitterData2.getRawDataUIDMap().keySet();
>>>         for (String uid : UIDs) {
>>>             g.addVertex(uid);
>>>         }
>>>
>>>         // add edges
>>>         long count = 0;
>>>         for (Tweet aTweet : twitterData2.getRawData()) {
>>>             String thisAuthor = aTweet.getAuthorId();
>>>
>>>             Collection<Tweet> result = query(thisAuthor)
>>>             for (Tweet tweet : result) {
>>>                 String thatAuthor = tweet.getAuthorId();
>>>                 Tweet[] pair = new Tweet[] { aTweet, tweet };
>>>                 Tweet[] pair1 = new Tweet[] { tweet, aTweet };
>>>
>>>                 if (!thisAuthor.equals(thatAuthor)) {
>>>
>>>                     try {
>>>                         List<Tweet[]> anEdge;
>>>                         if ((anEdge = g.findEdge(thisAuthor,
>>> thatAuthor)) == null) { // if there is no links between the two, then add a
>>> new one
>>>                             anEdge = new ArrayList<Tweet[]>();
>>>                             g.addEdge(anEdge , thisAuthor,
>>>                                     thatAuthor);
>>>                         }
>>>
>>>                         if (!(anEdge.contains(pair) ||
>>> anEdge.contains(pair1))) {
>>>                             anEdge.add(new Tweet[] { aTweet, tweet });
>>>                         }
>>>                     } catch (Exception e) {
>>>
>>>                         // TODO: handle exception
>>>                         count++;
>>>                         // e.printStackTrace();
>>>                         // if (!g.containsVertex(thisAuthor) ||
>>>                         // !g.containsVertex(thatAuthor))
>>>                         // return null;
>>>                         // for (List<Tweet[]> edge :
>>>                         // g.getIncidentEdges(thisAuthor))
>>>                         // g.getEdges().contains(edge);
>>>                         // if (g.getOpposite(thisAuthor,
>>>                         // edge).equals(thatAuthor))
>>>                         // System.out.println(edge.toString());
>>>                         // throw e;
>>>
>>>                     }
>>>
>>>                 }
>>>             }
>>>         }
>>>
>>>
>>>
>>> On Tue, Sep 24, 2013 at 6:22 PM, Joshua O'Madadhain <
>>> jos...@gm...> wrote:
>>>
>>>> Your report is confusing.  You start out talking about g.findEdge() and
>>>> then talk about the return collection you get from g.getIncidentEdges().
>>>>  Please post a self-contained snippet that has the problem you're
>>>> describing.
>>>>
>>>>
>>>> On Tue, Sep 24, 2013 at 4:05 AM, Han Qi <shm...@gm...> wrote:
>>>>
>>>>> Hallo guys, I am using JUNG in a project. I find sometimes  g.findEdge
>>>>> throw java.lang.NullPointerException.
>>>>> I find that for some edges I get from  g.getIncidentEdges(v),
>>>>> edges.get(edge) returns null.
>>>>> It is a bug?
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> October Webinars: Code for Performance
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>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> jos...@gm.........
>>>> sites.google.com/site/joshuaomadadhain/
>>>>    Joshua O'Madadhain: Information Scientist, Musician,
>>>> Philosopher-At-Tall
>>>> It's that moment of dawning comprehension that I live for.  -- Bill
>>>> Watterson
>>>>  My opinions are too rational and insightful to be those of any
>>>> organization.
>>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> October Webinars: Code for Performance
>>> Free Intel webinars can help you accelerate application performance.
>>> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most
>>> from
>>> the latest Intel processors and coprocessors. See abstracts and register
>>> >
>>>
>>> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
>>> _______________________________________________
>>> Jung-support mailing list
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>>>
>>
>>
>> ------------------------------------------------------------------------------
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>> Free Intel webinars can help you accelerate application performance.
>> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most
>> from
>> the latest Intel processors and coprocessors. See abstracts and register >
>>
>> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
>> _______________________________________________
>> Jung-support mailing list
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>> https://lists.sourceforge.net/lists/listinfo/jung-support
>>
>>
>
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most
> from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> Jung-support mailing list
> Jun...@li...
> https://lists.sourceforge.net/lists/listinfo/jung-support
>
>


-- 
jos...@gm.........sites.google.com/site/joshuaomadadhain/
   Joshua O'Madadhain: Information Scientist, Musician, Philosopher-At-Tall
It's that moment of dawning comprehension that I live for.  -- Bill
Watterson
 My opinions are too rational and insightful to be those of any
organization.