title: event driven simulation with objects
body: <p>i am writing an event driven simulation program. i have 3 subclasses that inherit 1 base class. i need to generate those three randomly and each subclass will go through different event path (sorry its a bit hard to describe what i meant), ill give an example:</p>
  
  <p>let say we have a car park simulation at a mall, we have the base class Vehicle, and subclasses Car, Motorbike, TruckContainer. the Car and Motorbike is just going to park for a period of time(random) and leave while TruckContainer need to park only for unloading and loading the container and leave, the number of container will decide how long the truck will park.</p>
  
  <p>how can i create those 3 objects randomly, let say 5-10 car will enter the car park in 1minute, 1-3 motorbike in 10minute, and only 1-2 truck container in a day?</p>
  
  <p>thank you</p>