我可以声明方法来返回Class对象，并限制Java中给定类型的子类吗？

Question

Suppose I declare some abstract method, that will return Class object (like Dog.class, Cat.class), like this:

abstract public Class getProducedAnimalType();

Can I force clients extending this API to return only Class objects that represents classes, wchich are subclassess of Animal.class ? something like:

abstract public Class<representing subclass of Animal> getProducedAnimalType();

So the client extending my class cannot write:

public Class getProducedAnimalType() {
   // Integer not extends Animal!, shoud not compile!
   return Integer.class; 
}

but can:

public Class getProducedAnimalType() {
   return Fish.class; // Fish extends Animal
}

Answer 1

You can change the return type Class to Class<? extends Animal> Class<? extends Animal> . The following code will allow to return Cat.class and Dog.class , but won't allow to return Integer.class :

abstract public Class<? extends Animal> getProducedAnimalType();

The client can write the following code and will compile fine:

public Class<? extends Animal> getProducedAnimalType() 
{
   return Fish.class; // Fish extends Animal
}

But the following code won't compile:

public Class getProducedAnimalType() 
{
   return Integer.class; 
}

Answer 2

public Class<? extends Animal> getProducedType() {
// return Integer.class; // compile time error: incompatible types
    return Dog.class;
}