Doubt in the output of this program.

[Pinki Roy]

class Mammal{
   void eat(Mammal m){
   System.out.println("Mammal eats food");
   }
}
class Cattle extends Mammal{
   void eat(Cattle c){
   System.out.println("Cattle eats hay");
   }
}

class Horse extends Cattle{
    void eat(Horse h){
    System.out.println("Horse eats hay");
    }
}
public class Test{
  public static void main(String[] args){
    Mammal h = new Horse();
    Cattle c = new Horse();
    c.eat(h);
  }
}
   

I don't understand why Mammal eats food is being displayed.

[Dan Drillich]

h is of type Mammal when eat is called. Therefore, eat(Mammal m) runs.

Regards,
Dan

[Arhaan Singhania]

Hi Pinki,

The methods are basically overloaded and choice of which overloaded method to call or the signature depends upon
reference type and signature. If you see the method is taking Mammal reference so it is calling the Mammal eating
Hay. I guess this is the correct answer.

Arhaan

[Mezan Shareef]

Arhaan Singhania wrote:Hi Pinki,

The methods are basically overloaded and choice of which overloaded method to call or the signature depends upon
reference type and signature. If you see the method is taking Mammal reference so it is calling the Mammal eating
Hay. I guess this is the correct answer.

Arhaan

Hi Arhaan

I dont see methods overloaded, eat method have only one parameter, they are overridden. but, i think, h is of type mamal, so mamal code is excuted. I did not execute the code though, just guessing.

[foxy milano]

Mezan Shareef wrote:

Arhaan Singhania wrote:Hi Pinki,

The methods are basically overloaded and choice of which overloaded method to call or the signature depends upon
reference type and signature. If you see the method is taking Mammal reference so it is calling the Mammal eating
Hay. I guess this is the correct answer.

Arhaan

Hi Arhaan

I dont see methods overloaded, eat method have only one parameter, they are overridden. but, i think, h is of type mamal, so mamal code is excuted. I did not execute the code though, just guessing.

hi mezan i think that arhaan is right... if you read katy and bert book about rule of overriding, they said that :"The argument list must exactly match that of the overridden method. If they
don't match, you can end up with an overloaded method you didn't intend"
the problem here is this : Mammel is a parent of Cattle and cattle is the parent of Horse
so Horse inherit all eat() method from Mammel and Cattle
Cattle inherit eat() method from Mammel
so if you call the eat method from Horse object and pass a Cattle or Mammel reference , it will call the Cattle or Mammel eat method because Horse object inherit them.
regards.

[Zeeshan Sheikh]

Mamal eats food because 'h' is of type Mammal so Mammal's class eat method is called.

Hope this helps.

[Rajat kumar jain]

hI PINKY ROY

Polymorphism does not work in Overloading functions and therefore it is decided at compile time which version to call of overloaded functions. And since the compiler is concerned only with reference type therefore it will see that you are calling the method with Mammal as an argument and thus it will call mammal version of the method. If you have some another query please post it here.

[Arhaan Singhania]

Hi,
I totally agree with foxy explanation. Hope this helps.
Thanks,
Arhaan

[navneet kumarbairwal]

Mezan Shareef wrote:

Arhaan Singhania wrote:Hi Pinki,

The methods are basically overloaded and choice of which overloaded method to call or the signature depends upon
reference type and signature. If you see the method is taking Mammal reference so it is calling the Mammal eating
Hay. I guess this is the correct answer.

Arhaan

Hi Arhaan

I dont see methods overloaded, eat method have only one parameter, they are overridden. but, i think, h is of type mamal, so mamal code is excuted. I did not execute the code though, just guessing.

Methods are overloaded because although there is only one parameter but they are different.

[Mezan Shareef]

foxy milano wrote:

Mezan Shareef wrote:

Arhaan Singhania wrote:Hi Pinki,

The methods are basically overloaded and choice of which overloaded method to call or the signature depends upon
reference type and signature. If you see the method is taking Mammal reference so it is calling the Mammal eating
Hay. I guess this is the correct answer.

Arhaan

Hi Arhaan

I dont see methods overloaded, eat method have only one parameter, they are overridden. but, i think, h is of type mamal, so mamal code is excuted. I did not execute the code though, just guessing.

hi mezan i think that arhaan is right... if you read katy and bert book about rule of overriding, they said that :"The argument list must exactly match that of the overridden method. If they
don't match, you can end up with an overloaded method you didn't intend"
the problem here is this : Mammel is a parent of Cattle and cattle is the parent of Horse
so Horse inherit all eat() method from Mammel and Cattle
Cattle inherit eat() method from Mammel
so if you call the eat method from Horse object and pass a Cattle or Mammel reference , it will call the Cattle or Mammel eat method because Horse object inherit them.
regards.

Hi all, sory for replying soo late, i was busy last few days. I understood that method is taking Mammal reference so it calls that Sys.out. I agree. But i still do not no, why are you all saying, it is overloaded method. I am sure i might be wrong, but it has only one parameter so it is overridden, and not overloaded. I am still missing something, may be, because you all say it is overloaded method.

Overloaded Method: has multiple parameters,
OverRidden Methods: has same # of parameters.

[Hari Krishna]

Hi Mezan,

For Overloaded Method, there will be change in method signature
But in Overriding Method, there won't be any change.

See the below link you can understand easily:
http://docs.oracle.com/javase/tutorial/java/javaOO/methods.html

Cheers,
Hari krishna

[Mezan Shareef]

Hari Krishna wrote:Hi Mezan,

For Overloaded Method, there will be change in method signature
But in Overriding Method, there won't be any change.

See the below link you can understand easily:
http://docs.oracle.com/javase/tutorial/java/javaOO/methods.html

Cheers,
Hari krishna

Hi

Thankyou Hari Krishna, i got it.