var nonMath = function(){
    var num = 2;
    print("num : " + num); //prints 2
    return (num);
};

var doMath = function(){
    var num = Math.round(2.0);
    print("num : " + num); //prints 2
    return (num);
};

ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
engine.eval(new FileReader("lib/script.js"));

Invocable invocable = (Invocable) engine;
System.out.println("nonMath : " + invocable.invokeFunction("nonMath")); //prints 2
System.out.println("doMath : " + invocable.invokeFunction("doMath")); //prints 2.0