What are some examples of contravariance in Java?

Can you explain contravariance in Java with examples?

Sure! Contravariance allows a method to accept arguments of a more general type than specified. For example, if you have a class Animal and a subclass Dog, a method that takes an Animal can also accept a Dog.

Can you give a specific code example?

Absolutely! Here's a simple example:

class Animal {}
class Dog extends Animal {}

class AnimalHandler<T extends Animal> {
    void handle(T animal) {
        System.out.println("Handling animal: " + animal);
    }
}

class DogHandler extends AnimalHandler<Dog> {
    void handle(Dog dog) {
        System.out.println("Handling dog: " + dog);
    }
}

In this case, DogHandler can handle Dog objects, which are a specific type of Animal.

What about using contravariance with interfaces?

Great question! With interfaces, you can use contravariance by defining a method that accepts a supertype. For example:

interface Handler<T> {
    void handle(T t);
}

class AnimalHandler implements Handler<Animal> {
    public void handle(Animal animal) {
        System.out.println("Handling animal: " + animal);
    }
}

class DogHandler implements Handler<Dog> {
    public void handle(Dog dog) {
        System.out.println("Handling dog: " + dog);
    }
}

Here, AnimalHandler can handle any Animal, while DogHandler is specific to Dog.

Thanks! This really helps clarify contravariance.

You're welcome! I'm glad I could help. If you have more questions about Java or programming concepts, feel free to ask!