Java Covariants

class Animal {}
class Cat extends Animal {}

class Container<T> {
    public void set(T value) {
        // ...
    }
}

class AnimalContainer extends Container<Animal> {
    public void set(Animal value) {
        // ...
    }
}

class CatContainer extends Container<Cat> {
    public void set(Cat value) {
        // ...
    }
}

class Animal {}
class Cat extends Animal {}

class Example {
    public Animal getAnimal() {
        // ...
    }

    public Cat getCat() {
        // ...
    }
}