I need to make default scale of
MapView map = new MapView(this, MapRenderMode.VECTOR);
twice as large (zoom in). I'm using Android Java, no JS
If you want to zoom in by 2x each time, zoom level is appropriate. Each zoom level is 2x the previous one. For your map instance:
map.setScene(MapScene.createFromLocationAndZoomLevel(map.getCenter(), map.getZoomLevel + 1), MapAnimationKind.LINEAR);