Covariant returns

[C Kushtawar]

This is a simple program that I have written:

    class Animal {
	long doSt(float b) {
		return 5;
	}
}


class Cat extends Animal {
	int doSt(float b) {//compilation fails here ?
		return 64;
	}
	
}

But the same program compiles fine when the return types are of Object types as below :

  

class Animal {
	Animal doSt(float b) {
		return new Cat();
	}
}


class Cat extends Animal {
	Cat doSt(float b) {
		return new Cat();
	}
	
}

  

Why is it so?Please explain.

[Vierda Mila]

Kusthawar, the explanation is simple Cat is-a Animal so the covariant returns ok, but int is-a NOT long.
Hope it clear your doubt.

[Ravikanth kolli]

As vierda was talking about covariant returns, the return type of a method in subclass should be subclass of the return type of the method in the super class. Animal is a super class of cat so it works fine, but int is not a super class of long.