Another related class could be a truck, which would have similar fields, but not be exactly the same as a car. Both a car and a truck could be a kind of a third class which could be called a vehicle class. In this way, the programmer could create the parts of the program that are the same for both the car and the truck in programming the vehicle class, yet the programmer would be free to program how a car is different from a truck without duplicating all of the programming.