How to do it using Polymorphism now

[Caglar Cataloglu]

So;

I have lots of animal classes and a Cat class all extending Animal class. But i have a few more special functions just for cats, like sing() function. So how can i call sing function ?

void AnimalTest(Animal a)
{
  a.eat(); //no problem with that, all animals eat

  //if(a.equals cat object){
  //Cat c = new Cat();
  //a = (Cat)c;
  //call sing function
  }
}

[Caglar Cataloglu]

i think i should use 'instanceof' keyword. but do you think this is a good software design

[mukesh pandey]

you can use following code


void AnimalTest(Animal animal)
{
animal.eat(); //no problem with that, all animals eat
if(animal instanceof Cat){ // it check if the animal reference variable have cat as object or animal if cat then it allowes it to go in and the you can invoke sing menthod on cat
cat c = (cat)animal;
c.sing()

}
}

[Ram Narayan.M]

You can define the special functions in an "Interface". Rather restricting with "Cat" class, You can make "AnimalTest()" method generic one for animals which can sing.

[Campbell Ritchie]

That sounds a good idea about the interface, but maybe you would like to give links to tutorials about generic methods and interfaces.

[Shanky Sohar]

Caglar Cataloglu wrote:So;

I have lots of animal classes and a Cat class all extending Animal class. But i have a few more special functions just for cats, like sing() function. So how can i call sing function ?

void AnimalTest(Animal a)
{
  a.eat(); //no problem with that, all animals eat

  //if(a.equals cat object){
  //Cat c = new Cat();
  //a = (Cat)c;
  //call sing function
  }
}

i think instance of test will only solve your problem that your program will not throw any runtime exception
So,Remember
for overloaded method refernce type determine which method to call.
but for overridden methods objects type define determines which method to call.

As you are talking about polymorphism ,overloaded method doesnot comes into picture then,
so you can make an object of appropriate type to call your overridden method.

[Cody Long]

All you have to do is add the sing() method to the cat class.
For example:

public class Cat extends Animal {
   public void sing() {
      //stuff to make cat sing
   }
   ///other stuff in the Cat class
}  

The your AnimalTester method would look like this:

public void AnimalTester(Animal a) {
   a.eat();
   if (a.equals cat object) {
      Cat c = new Cat();
      a = (Cat) c;
      c.sing();
   }
}