Nasreddine

  import com.hp.hpl.jena.query.* ;
  Model model = ... ;
  String queryString = " .... " ;
  Query query = QueryFactory.create(queryString) ;
  QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
  try {
    ResultSet results = qexec.execSelect() ;
    for ( ; results.hasNext() ; )
    {
      QuerySolution soln = results.nextSolution() ;

Nasreddine

An interface is a contract (or a protocol, or a common understanding) of what the classes can do. When a class implements a certain interface, it promises to provide implementation to all the abstract methods declared in the interface. Interface defines a set of common behaviors. The classes implement the interface agree to these behaviors and provide their own implementation to the behaviors. This allows you to program at the interface, instead of the actual implementation. One of the main usage of interface is provide a communication contract between two objects. If you know a class implements an interface, then you know that class contains concrete implementations of the methods declared in that interface, and you are guaranteed to be able to invoke these methods safely. In other words, two objects can communicate based on the contract defined in the interface, instead of their specific implementation.

Secondly, Java does not support multiple inheritance (whereas C++ does). Multiple inheritance permits yo