A fix for the examples from JPL prolog java binding http://www.swi-prolog.org/packages/jpl/java_api/getting_started.html

demo.P

Variable X = new Variable("X");
Query q4 = 
    new Query( 
        "descendent_of", 
        new Term[] {X,new Atom("ralf")} 
    );

java.util.Hashtable solution;

solution = q4.oneSolution();

System.out.println( "first solution of descendent_of(X, ralf)"); 
System.out.println( "X = " + solution.get("X"));