// One could refine what to export with:
// Content c1 = univ.getContent(Display3D.makeTitle(b1)); // by title
// Content c2 = ...
// ... and then adding them to a Collection.
//
Image3DUniverse univ = Display3D.getDisplay(project.getRootLayerSet()).getUniverse();
Collection all = univ.getContents();
MeshExporter.saveAsWaveFront(all); // pops up file dialog to save
}