SPARQL ARQ Query Execution

Question

So I have this piece of Jena code, which basically tries to build a query using a Triple ElementTriplesBlock and finally using the QueryFactory.make(). Now I have a local Virtuoso instance set up and so my SPARQL end point is the localhost. i.e. just http://localhost:8890/sparql. The RDFs that I am querying are generated from the Lehigh University Benchmark generator. NowI am trying to replace the triples in the query pattern based on some conditions. i.e. lets say if the query is made of two BGPs or triple patterns and if one of the triple patterns gives zero results, I'd want to change that triple pattern to something else. How do I achieve this in Jena? . My code looks like

//Create your triples
Triple pattern1 = Triple.create(Var.alloc("X"),Node.createURI("http://www.w3.org/1999/02/22-rdf-syntax-ns#type"),Node.createURI("http://swat.cse.lehigh.edu/onto/univ-bench.owl#AssociateProfessor"));
Triple pattern = Triple.create(Var.alloc("X"), Node.createURI("http://swat.cse.lehigh.edu/onto/univ-bench.owl#emailAddress"), Var.alloc("Y2"));

ElementTriplesBlock block = new ElementTriplesBlock();
block.addTriple(pattern1);
block.addTriple(pattern);

ElementGroup body = new ElementGroup();
body.addElement(block); 

//Build a Query here

Query q = QueryFactory.make();
q.setPrefix("ub", "http://swat.cse.lehigh.edu/onto/univ-bench.owl#");

q.setQueryPattern(body);

q.setQuerySelectType();
q.addResultVar("X");

//?X ub:emailAddress ?Y2 .  
//Query to String
System.out.println(q.toString());



QueryExecution qexec = QueryExecutionFactory.sparqlService("http://localhost:8890/sparql", q);
Op op = Algebra.optimize(Algebra.compile(q));
System.out.println(op.toString());

So to be clear I am able to actually see the BGP in a Relational Algebra form by using the Op op = Algebra.optimize(Algebra.compile(q)) line. The output looks like

(project (?X)
  (bgp
    (triple ?X <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://swat.cse.lehigh.edu/onto/univ-bench.owl#AssociateProfessor>)
    (triple ?X <http://swat.cse.lehigh.edu/onto/univ-bench.owl#emailAddress> ?Y2)
  ))

Now how would I go about evaluating the execution of each triple? In this case, if I just wanted to print the number of results at each step of the query pattern execution, how would I do it? I did read some of the examples here. I guess one has to use an OpExecutor and a QueryIterator but I am not sure how they all fit together. In this case I just would want to iterate through each of the basic graph patterns and then output the basic graph pattern and the number of results that it returns from the end point. Any help or pointers would be appreciated.