Get MLDesktop instance from Java MatlabEngine

I'm trying to do some operations on the Matlab GUI from an external Java class. For this I need the current instance of MLDesktop, and following various examples I tried something like this

import com.mathworks.engine.*;
import com.mathworks.mde.desk.*;
import java.io.*;

public class javaMatlabConnect {
    public static void main(String[] args) throws Exception {
        String myEngine = "myMatlabEngine";
        MatlabEngine eng = MatlabEngine.connectMatlab(myEngine);

      MLDesktop jDesktop = eng.feval("com.mathworks.mde.desk.MLDesktop.getInstance"); // << This is where I get an error
        // DO STUFF
        eng.close();
      }
  }

This code sadly doesn't work: I get the exception

UnsupportedTypeException: Data Conversion Error for type: com.mathworks.mde.desk.MLDesktop

on the marked line. Probably there is a smarter way to do this, but I thought that my code should have worked.

Does anybody have a suggestion?

P.S.: I decompiled the com.mathworks.engine library, but I didn't see anything that could help me.