Hello Lorenz, sorry to bother you.
What if we use
RDFNode physicsBestCat=indiv.getPropertyValue(bestcat);
if (null!=phsicsBestCat) {
Literal l1=physicsBestCat.asLiteral();
String s1=l1.toString();}
In fact, I tried this and it does not give exception, but dont know about
the correct result.
Regards
On Tue, Jan 17, 2017 at 4:30 PM, Sidra shah <[email protected]> wrote:
> Hi Lorenz, I am sorry but with much regards, you discussed here the
> problem, not the solution :) :)
>
> I know this if there is no value, there must be Null exception, but can
> you suggest me a way where we dodge the compiler and it skip the lines when
> there is no value.
> I know this is more a Java problem, but any help I will appreciate.
>
> Regards
>
> On Tue, Jan 17, 2017 at 4:20 PM, Lorenz B. <[email protected]
> leipzig.de> wrote:
>
>> no no no, I told you that the method getPropertyValue(p) can return NULL
>> if there is no such value for the given property p
>>
>> That means what for your line
>>
>> RDFNode physicsBestCat=indiv.getPropertyValue(bestcat);
>>
>> ?
>>
>> Right, physicsBestCat can be NULL.
>>
>> That means what for your line
>>
>> Literal l1=physicsBestCat.asLiteral();
>>
>> ?
>>
>> Right, asLiteral() must not be called if physicsBestCat is NULL.
>>
>> > I mean Lorenz, is there any way, if there is no value, it do nothing (do
>> > not give exception) and if there is value, it should simply give us the
>> > value.
>> >
>> > if (l1!=null) supposed to work. :)
>> >
>> > Is it possible if we use something
>> >
>> > if (li==null)
>> > break;
>> >
>> > And we should get out of this snippet?
>> >
>> > Regards
>> >
>> > On Tue, Jan 17, 2017 at 4:10 PM, Lorenz B. <
>> > [email protected]> wrote:
>> >
>> >> ???
>> >>
>> >> if there is no such value you can't get the value, I do not see the
>> problem
>> >>> Hello Lorenz, thanks.
>> >>>
>> >>> Is there any way (alternative) to get this value as I need it further
>> in
>> >> my
>> >>> operation?
>> >>>
>> >>> Regards
>> >>>
>> >>> On Tue, Jan 17, 2017 at 4:03 PM, Lorenz B. <
>> >>> [email protected]> wrote:
>> >>>
>> >>>>> Hello Lorenz, believe me I have tried this before I write my problem
>> >> here
>> >>>>> in the forum but the problem persists. I also tried if s1!=null. .
>> >>>>>
>> >>>>> RDFNode physicsBestCat=indiv.getPropertyValue(bestcat);
>> >>>> But then the NullPointerException already occurs here.
>> >>>>
>> >>>> getPropertyValue can return NULL if there is no such value, that's
>> also
>> >>>> explained in the Javadoc
>> >>>>> Literal l1=physicsBestCat.asLiteral();
>> >>>> You can't do it if physicsBestCat can be NULL
>> >>>>> if (l1!=null){
>> >>>>> String s1=l1.toString();
>> >>>>>
>> >>>>> if (s1=="Physics"){
>> >>>>> }}
>> >>>>>
>> >>>>> Regards
>> >>>>>
>> >>>>> On Tue, Jan 17, 2017 at 3:48 PM, Lorenz B. <
>> >>>>> [email protected]> wrote:
>> >>>>>
>> >>>>>> Sorry, but the answer is too obvious, especially for a student in
>> >>>>>> computer science.
>> >>>>>>
>> >>>>>> What about checking if the literal is NULL before calling
>> toString()?
>> >>>>>>
>> >>>>>>> Hello, I asked about this rule few days ago.
>> >>>>>>> String rule ="[rule1: ( ?x http://www.semanticweb.org/t/o
>> >>>>>>> ntologies/2016/7/myOWL#Physics_Preferred_Category ?cat1 )" +
>> >>>>>>> "( ?x http://www.semanticweb.org/t/o
>> ntologies/2016/7/myOWL#Chem_Pr
>> >>>>>>> eferred_Category ?cat2 )" +
>> >>>>>>> // "( ?x http://www.semanticweb.org/t/o
>> >>>>>>> ntologies/2016/7/myOWL#Geo_Preferred_Category ?cat3 )" +
>> >>>>>>> // "greaterThan(?cat1,?cat2), greaterThan(?cat1,?cat3)"
>> >>>>>>> + " -> (?x http://www.semanticweb.org/t/
>> >>>>>>> ontologies/2016/7/myOWL#BestCategory
>> http://www.semanticweb.org/t/
>> >>>>>>> ontologies/2016/7/myOWL#BestCategory#Physics )]";
>> >>>>>>>
>> >>>>>>> The BestCategory is saved but as you know a user will select all
>> the
>> >>>>>> three
>> >>>>>>> categories in the quiz, then the rule will execute, otherwise the
>> >> user
>> >>>>>> the
>> >>>>>>> user will have not the property BestCategory.
>> >>>>>>>
>> >>>>>>> When I want to extract the value of BestCategory for some
>> operation,
>> >>>> for
>> >>>>>>> first time users to the quiz, it gives me Null Pointer Exception,
>> and
>> >>>>>>> rightly so because the user has no value of BestCategory.
>> >>>>>>>
>> >>>>>>> RDFNode physicsBestCat=indiv.getPropertyValue(bestcat);
>> >>>>>>> Literal l1=physicsBestCat.asLiteral();
>> >>>>>>>
>> >>>>>>> //*here I think is the exception is*
>> >>>>>>> String s1=l1.toString();
>> >>>>>>>
>> >>>>>>> if (s1=="Physics"){
>> >>>>>>> }
>> >>>>>>>
>> >>>>>>> How should I handle this problem please?
>> >>>>>>>
>> >>>>>>> Much regards
>> >>>>>>>
>> >>>>>> --
>> >>>>>> Lorenz Bühmann
>> >>>>>> AKSW group, University of Leipzig
>> >>>>>> Group: http://aksw.org - semantic web research center
>> >>>>>>
>> >>>>>>
>> >>>> --
>> >>>> Lorenz Bühmann
>> >>>> AKSW group, University of Leipzig
>> >>>> Group: http://aksw.org - semantic web research center
>> >>>>
>> >>>>
>> >> --
>> >> Lorenz Bühmann
>> >> AKSW group, University of Leipzig
>> >> Group: http://aksw.org - semantic web research center
>> >>
>> >>
>> --
>> Lorenz Bühmann
>> AKSW group, University of Leipzig
>> Group: http://aksw.org - semantic web research center
>>
>>
>
