Generics vs Class<?>

Question

Is it possible to get implement the class from the generic for type casting for example this fail for me buildingObject.tojava(S) in below example

public abstract class AbstractPythonService implements FactoryBean<IHelloService> {

    public IHelloService getObject() {

        //Here is the actual code that interprets our python file.
        PythonInterpreter interpreter = new PythonInterpreter();
        interpreter.execfile("src/main/python/HelloServicePython.py");
        PyObject buildingObject = interpreter.get("HelloServicePython").__call__();


        //Cast the created object to our Java interface
        return (IHelloService) buildingObject.__tojava__(IHelloService.class);
    }

    @Override
    public Class<?> getObjectType() {
        return IHelloService.class;
    }
}

I want something like this

public abstract class AbstractPythonService<S> implements FactoryBean<S> {

    public S getObject() {

        //Here is the actual code that interprets our python file.
        PythonInterpreter interpreter = new PythonInterpreter();
        interpreter.execfile("src/main/python/HelloServicePython.py");
        PyObject buildingObject = interpreter.get("HelloServicePython").__call__();


        //Cast the created object to our Java interface
        return (S) buildingObject.__tojava__(S.class);
    }

    @Override
    public Class<?> getObjectType() {
        return S.class;
    }
}

Answer 1

Because of type erasure you need a Class<S> object, some Xyz.class.

public abstract class AbstractPythonService<S> implements FactoryBean<S> {
    private final Class<S> type;

    protected AbstractPythonService(Class<S> type) {
        super(type); // Probably the factory would also need the type.
        this.type = type;
    }

    return type.cast(buildingObject.__tojava__(type)); // type.cast probably unneeded.

public Class<S> getObjectType() {
    return type;
}