Interfaces and Comparable-CodePudding

i'm beginner and just learning abstract classes and interfaces but really struggeling to get it right.

MY Class structure.

Abstract Class Vehicle
Class Car (extends Vehicle, implements ITuning)
Class Motorcycle (extending Vehicle)
Interface ITuning

I want to have an abstract method doRace() that I can use in my Car class to compare the Car Objects (car.getHp()) and prints the winner. I try to implement a doRace(object o) into the Interface ITuning and a doRace(Car o) into my Car class but get the error. How can I implement that correctly ?

The type Car must implement the inherited abstract method ITuning.doRace(Object)

But if do chage it to Object, i can't use it in my Car class…

public interface ITuning
{
abstract void doRace(Object o1);
}

public Car extends Vehicle implements ITuning
{
 public void doRace(Car o1){
 if(this.getHp() > o1.getHp())
 };
}

Any Idea what i'm doing wrong? I assume its a comprehension error

CodePudding user response：

You can make ITuning generic.

public interface ITuning<T> {
  
  void doRace(T other);
}

Implementation will be like this:

public class Car extends Vehicle implements ITuning<Car> {

  @Override
  public void doRace(Car other) {
    //do comparison
  }
}

Implementation in other classes will be quite similar, just change the generic parameter.

As a side note, i would rename the interface to something more fitting. Considering that tuning a vehicle is the act of modifying it to optimise its' performance, ITuning providing functionality to do the actual racing is counter intuitive.

CodePudding user response：

You can change your ITuning interface to

public interface ITuning
{
    void doRace(Vehicle other);
}

Since Vehicle defines the getHp() method this ensures that your actual implementation can access it.

The difference to Chaosfire's answer is that this will allow you to do a race between different types of vehicles, e.g. a Car and a Motorcycle, while the generic ITuning<T> class will be limited to races between equal types*.

Chaosfire's point regarding the interface name is still valid.

*This is a bit over-simplified to make my point clearer. Of course Car could implement ITuning<Car> and ITuning<Motorcycle> but this may not be what you want.