Own Application Class in RCP is not called - eclipse

Question

I develop a Eclipse RCP Client with the 2019-06 Eclipse Framework.
My aim is it to override the IDEApplication class from the eclipse core, because I would like to force the workspace choose prompt to pop up at every start. In the eclipse class are some coditions which creates problems in my application. This is the reason why I want to override the class. My problem is now that my application class is not called at the startup of the product.
This is my application class.
import org.eclipse.equinox.app.IApplication;
import org.eclipse.equinox.app.IApplicationContext;
import org.eclipse.swt.widgets.Display;
import org.eclipse.ui.IWorkbench;
import org.eclipse.ui.PlatformUI;
/**
* This class controls all aspects of the application's execution
*/
public class Application implements IApplication {
/*
* (non-Javadoc)
*
* #see org.eclipse.equinox.app.IApplication#start(org.eclipse.equinox.app.IApplicationContext)
*/
#Override
public Object start(IApplicationContext context) throws Exception {
Display display = PlatformUI.createDisplay();
Location instanceLoc = Platform.getInstanceLocation();
boolean isWorkspaceSelected = false;
try {
URL url = new File(System.getProperty(“user.home”), “workspace”).toURI().toURL();
ChooseWorkspaceData data = new ChooseWorkspaceData(url);
ChooseWorkspaceDialog dialog = new ChooseWorkspaceDialog(display.getActiveShell(), data, true, true);
dialog.prompt(true);
String selection = data.getSelection();
if (selection != null) {
isWorkspaceSelected = true;
data.writePersistedData();
url = new File(selection).toURI().toURL();
instanceLoc.set(url, false);
}
} catch (Exception e) {
throw new RuntimeException(e);
}
try {
if (isWorkspaceSelected) {
int returnCode = PlatformUI.createAndRunWorkbench(display, new ApplicationWorkbenchAdvisor());
if (returnCode == PlatformUI.RETURN_RESTART)
return IApplication.EXIT_RESTART;
}
return IApplication.EXIT_OK;
} finally {
display.dispose();
}
}
/*
* (non-Javadoc)
*
* #see org.eclipse.equinox.app.IApplication#stop()
*/
#Override
public void stop() {
if (!PlatformUI.isWorkbenchRunning())
return;
final IWorkbench workbench = PlatformUI.getWorkbench();
final Display display = workbench.getDisplay();
display.syncExec(new Runnable() {
#Override
public void run() {
if (!display.isDisposed())
workbench.close();
}
});
}
}
Now I have two questions.
If I debug my application this class is never in the callstack. What do I have to do that this class is started ?
Is there a other way to force the prompt for choosing a workspace location at the start of the application than to override this class ?
My main problem is that the original class of the core has the following condition:
if workspace is not set -> create dialog if workspace is already set -> dont create the dialog.
Unfortunatly in my application the workspace location is already set in the internal of eclipse beofre the core of eclipse is loaded.
I have already tried to change the start order of the plugins but that hasn´t helped.