error : Unable to cast object of type 'System.Int32' to type 'java.lang.Integer'

Hi I am trying to integrate Gephi( Visualisation tool) with Dot.

Since gephi is built on Java, and there are some functions which is asking gephi as input...

I have written below code which is compiled successfully. These classes belong to Gephi..

But i am getting error : Unable to cast object of type 'System.Int32' to type 'java.lang.Integer'on the last line..Any help is apriciated.

 Class objpreviewController = typeof(PreviewController);
                    PreviewController previewController = (PreviewController)Lookup.getDefault().lookup(objpreviewController);
                    PreviewModel model = previewController.getModel();
                    PreviewProperties props = model.getProperties();
                    props.putValue("width", 800);
                    props.putValue("height", 600);
                    ProcessingTarget target = (ProcessingTarget)previewController.getRenderTarget(RenderTarget.__Fields.PROCESSING_TARGET, workspace1);