Tutorials : The Pitfalls of Inheritance :

Modifying the Super Class Behavior…

public class Vehicle

{

   public void stop()

   {

       //stop the engine

 

   }

 

public void accelarate()

   {

       

   }

}

 

 

public class Car extends Vehicle

{

 

    public Car()

    {

 

    }

 

    public void stop()

    {

        //stop the engine

        //lock the steering wheel

    }

 

  public void switchOnWiper()

    {

        

    }

 

}

In this example, we have modelled Car IS A Vehicle. The Car class overrides the stop() method implementation of its super class Vehicle. However, it decides to reuse the accelarate() implementation from its super class.

As a result of this inheritance relationship, we will be able to write a VehicleTester class in the following form.

public class VehicleTester

{

    

    public void testVehicle(Vehicle vechicle)

    {

        //test the accelarate behaviour

        vechicle.accelarate();

        //test the stop behaviour

        vechicle.stop();

    }

 

}

In this example, you can immediately see the benefits of inheritance relationship. We could write a single method accepting a super class type and we are able to pass any sub class to the same method. This greatly reduces the strongly typed nature of code and increases the flexibility of the application module.

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