CODEWITHSUNDEEP
javainheritancepolymorphism
chris123
chris123

Reputation: 197

Polymorphism and Parameters?

So I understand that due to polymorphism one is allowed to do: Superclass Apt = new Subclass(); But I was wondering in the case of: 

Superclass Abc = new Subclass(); 
do(Abc);
void doThat(Superclass Abc)
   Abc.Ball();

So in the Abc.method call inside the method doThat, does this make a call to the Ball method of the Superclass or does it make a call to the Ball method of the Subclass (assuming that the subclass has overridden the Ball method). If it does make a call to the overridden Ball method of the Subclass, why can we just not make the method doThat be: void doThat(Subclass Abc) instead. Thanks for the help and I'll clarify more if it doesn't make sense.

Upvotes: 1

Views: 203

Answers (4)

Anderson Vieira
Anderson Vieira

Reputation: 9049

does this make a call to the Ball method of the Superclass or does it make a call to the Ball method of the Subclass

The call Abc.Ball() will call the overriden method in the subclass.

If it does make a call to the overridden Ball method of the Subclass, why can we just not make the method doThat be: void doThat(Subclass Abc) instead

Imagine you have two subclasses of Superclass:

Superclass abc = new SubclassA();
Superclass xyz = new SubclassZ();

Defining void doThat(Superclass abc) means that the method doThat() will accept any object that is an instance of Superclass or any of its subclasses. Then you could do doThat(abc) and doThat(xyz) and both would call the Ball() method in the appropriate instances.

In contrast, if you had doThat(SubclassA abc), you would also need a specific method for each subclass of Superclass, like doThat(SubclassZ xyz).

Upvotes: 1

Isuru Gunawardana
Isuru Gunawardana

Reputation: 2887

It's calling the overridden method that's the method overriding is for.

void doThat(Subclass Abc)

if you use Subclass here you can only pass Subclass instance to this. Instead if you have 

void doThat(Superclass Abc)

Then you can pass any object which implements Superclass That's where the polymorphism comes. doThat method accepts many type of objects, only requirement is it should implerments Superclass.

If I explained further, Lets say you have two Subclass called, Subclass1 and Subclass2 and these are implementation of Superclass where the Superclass is an interface. (These Subclasses should implements Superclass method definitions, therefore both subclasses has ball method)

Then whatever the instance come to the doThat method it calls the ball method of the corresponding object. As the void doThat(Superclass Abc) accept Superclass type.

Upvotes: 2

Codor
Codor

Reputation: 17605

In the situation you describe, the call

Abc.Ball();

will call the implementation in Subclass.

Upvotes: 0

SMA
SMA

Reputation: 37023

If the Ball method is static, it will call on super class as Ball method is defined at class level while if it's defined at object level, then definitely it will call overridden method on sub class.

Upvotes: 1

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