code: @Override
      public RepositoryResult<Resource> getContextIDs() throws RepositoryException {
          try{
              TupleQuery tupleQuery = prepareTupleQuery(QueryLanguage.SPARQL, ALL_GRAPH_URIS);
              TupleQueryResult result = tupleQuery.evaluate();
              return
                      new RepositoryResult<Resource>(
                              new ExceptionConvertingIteration<Resource, RepositoryException>(
                                      new ConvertingIteration<BindingSet, Resource, QueryEvaluationException>(result) {
  
                                          @Override
                                          protected Resource convert(BindingSet bindings)
                                                  throws QueryEvaluationException {
                                              return (Resource) bindings.getValue("g");
                                          }
                                      }) {
  
                                  @Override
                                  protected RepositoryException convert(Exception e) {
                                      return new RepositoryException(e);
                                  }
                              });
  
          } catch (MalformedQueryException e) {
              throw new RepositoryException(e);
          } catch (QueryEvaluationException e) {
              throw new RepositoryException(e);
          }
      }
docs: returns list of graph names as Resource
  
  @throws RepositoryException