Question

Say I have two classes

class Driver{
    //attributes of driver ,ex: driving licence number
    // methods related to driving ,ex: drive(Car) , stop(Car)
    changeTyre(Car,Tyre);   // sometimes the driver can change the tyres right?
}
class Mechanic{
    // Hard mechanical stuff , ex: repairEngine(Car)
    changeTyre(Car,Tyre);  // Simple.hence sometimes the driver also does
}

Now the implementations of the two changeTyre() methods will be the same.

Now I have two issues,

1. There is a repetition (duplication) of code
2. It doesn’t seem meaningful to have a Super class containing the changeTyre(Car,Tyre) method

How these kind of situations handled?

Answer 1

To expand on using composition over inheritance (Willie’s answer), I think you were on the right track in your comment about using ChangeTyre like car.ChangeTyre(Tyre).

Each mechanic or driver will be associated to a car, so they can have a Car property –

class Driver{

    Car driverCar;

    //constructor
    Driver(Car car)
    {
        driverCar = car;
    }

    //attributes of driver ,ex: driving licence number
    // methods related to driving ,ex: drive(Car) , stop(Car)
    changeTyre(Tyre) 
    {
        driverCar.changeTyre(Tyre);
    }
}

They changeTyre method of Driver and Mechanic might be the same, but the actual logic to change the tyre will live in one place. I don’t think inheritance works because a mechanic is not a driver, and inheritance supports an “is-a” relationship. It may not make sense to force changeTyre to a superclass (say Person), because not every class that inherits from Person would need to have a changeTyre method. See this question for more information about composition over inheritance.