Identify best suitable vehicle for an order

I am trying to use jsprit for order management i.e. order is assigned to best suited vehicle. First i identified 5 closest vehicles to pickup location through graphoper now i want assign that order to selected vehicles which may already be taking an order.

A per my understanding i have to first compute cost matrix using graphhoper then supply calculated value to jsprit algorithm which algo will be best suited for this and how can i fix the job(order) which he is currently executing.

I also asked the same question on stackoverflow but it was down voted

You can use,
vrpBuilder.addInitialVehicleRoutes()