Doubt Regarding Polymorphism

[vipul bondugula]

Hi ,

I am having a doubt regardig polymorphism. I have a base class Animal.child class Dog.

Ex:-Animal a = new Dog();

What this statement tells?In real time where this situation will occur...

Thanks in Advance,
Vipul.

[Ashwin Sridhar]

you are creating the dog object and giving it to a animal reference.
Such situation might occur when you create List Object.
List is a interface , so you create a Object for arrayList or any of the classes that implements List and referenc it to List .

List l = new ArrayList();

[vipul bondugula]

Thanks Ashwin,

This answer iam expecting. Actually my doubt starts here.we can directly write
ArrayList al = new ArrayList();
instead of
List l = new ArrayList();
What is the use in instantiating ArrayList and giving reference to List.?

Thanks in Advance,
Vipul.

[Seetharaman Venkatasamy]

Typically, It is better to program with super class/interface reference, this avoid the a class specific implementation method call in your code. for example,
pretend you love Dog now,

Animal animal = new Dog();
animal.sound();

after some time you decided to go for a cat since you dont like the Dog

Animal animal = new Cat();//this only one line modified!
animal.sound();

if you could have been used like this

Dog animal = new Dog();
animal.bark();---->(1)

in(1), you may tempted to use Dog class specific method, later when you change Dog to Cat
you are required to change the line (1) also , so totally two lines are modified, so maintenance may be nightmare there!

Cat animal = new Cat();//line modified
animal.meow();//line modified

this is a small example with two lines, think about thousands of line!

[vipul bondugula]

Thanks Seetharaman ,

Is this the only reason or any other logical reason. When i see that kind of statements iam confused a little bit.

and this is called as Run-time polymorophism,right?

can anyone tell me a real time example of this run-time polymorphism.

Thanks in Advance,
Vipul

[Seetharaman Venkatasamy]

look at this hot thread!

[Seetharaman Venkatasamy]

also, Please SearchFirst

[vipul bondugula]

Thanks Seetharaman,

I got my answer here.

"Polymorphism is defined as one interface to control access to a general class of actions."

This answer supports what you have said...Thank you for your suggestions..

Thank you.

[Seetharaman Venkatasamy]

vipul bondugula wrote:Thanks Seetharaman

you are welcome

[Seetharaman Venkatasamy]

vipul bondugula wrote:
"Polymorphism is defined as one interface to control access to a general class of actions."

Sorry for the late reply! I suggest you to read this