How can you indicate the return values of either the current class type or any of its subtypes through typing?

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In order to indicate the return values of either the current class type or any of its subtypes through typing, you can use the concept of covariant return types. This allows you to declare a method in a superclass that returns an object of that superclass, but then override that method in a subclass to return an object of a subclass, as long as the subclass is type-compatible with the superclass.

To do this in practice, you can declare the return type of the superclass method as the superclass itself, and then use the @Override annotation on the subclass method with the more specific return type. For example:

class Animal {
  public Animal reproduce() {
    return new Animal();
  }
}

class Mammal extends Animal {
  @Override
  public Mammal reproduce() {
    return new Mammal();
  }
}

In this example, the Animal class has a reproduce() method that returns an Animal object, but the Mammal subclass overrides this method with a more specific type, returning a Mammal object instead. This is allowed because Mammal is a subtype of Animal, and so the return type of the Mammal method is still compatible with the Animal method's return type.

By using covariant return types in this way, you can indicate the return values of a method as either the current class or any of its subtypes, while still maintaining the type hierarchy and ensuring type safety.