public SimulationEvent(int eventType, Object eventData)
    {
        if (eventType != EVENT_SIM_STARTED
            && eventType != EVENT_SIM_DONE
            && eventType != EVENT_SIM_CANCELLED
            && eventType != EVENT_SIM_ERROR
            && eventType != EVENT_SIM_PROGRESS
        ) {
            throw new IllegalArgumentException("Invalid event type");
        }
        
        this.eventType = eventType;
        this.eventData = eventData;
    }