Aggregation And Inheritence

[Dipti Mishra]

Hi,

I want a clear explanation about the difference between Inheritence and Aggregation along with a small code example.
Can anyone help me

Regards,
Dipti

[Sonali Salunkhe]

HI,
Aggregation : Containment.. One objcet acts like part of another onject.

Inheritance : U get properties from super class(existent class )
like parent & children

[harish shankarnarayan]

Hi Sonali,

Aggregation : Containment.. One objcet acts like part of another onject

Can u explain this point in brief with example
i didnt get it.

[Swati Thorve]

There r 2 ways by which we can access the methods or variables declared in another class

1> simply extend that class
e.g.

class A extends B{
//lot of code which accesses methods of class B as these are the methods from class A//
}

This is called Inheritance

2> In second way,we can declare the object of reqired class in our class,& then using that object access the methods of that class
e.g.
class B{}
Class A{
B b = new B();
//then here using b.methodname we can access the methods from class B
}

This is called Aggregation

[kotha vijaybabu]

hi harish and swati,

u explained abt aggregation and inheritance very well

i have seen a question like is-a,has-a relations belongs to inheritance and aggregation how? can anybody explain

thanx in advance

[Edisandro Bessa]

Hi Kotha,

I'll try explain using code.

IS-A Relationships

It's related to inheritance, ie, whenever you have a class that "extends" another class it will pass the "instanceof" check.

Imagine that a Ferrari is a car so ...

public class Car {
    public void accelerate(){}
    public void break(){}
 
    // ... Any other methods common to any car
}
 
public class Ferrari extends Car {
    public void fastenAutomaticSeatBealt(){}
    public void alertHighSpeed(){}
 
    // ... Any other Ferrari specific methods
}

HAS-A Relationships

It's related to object contents, ie, any other instance or class members that refers to another class (from same type or not).

Now, let me make a littler changes in our car ...

public class Car {
    //Any car has a ...
 
    Bumper bumper; // Instance member that refers to other class
    Wheel wheel;
    FrontLight frontLight;
    BackLight backLight;
    Door door;
 
    // And so on ...
}

[kotha vijaybabu]

thanx edisandro

i got it

thanx a lot

[levani dvalishvili]

I think, there is also a offset type of aggregation called composition
which basically means same thing but difference is more on conceptual level

--- AGREGATION ----
class  PublicGarage {
 
Car honda;
Car Toyota ;
etc ...
}

--- COMPOSITION ----
Automobile{
 
Engine aEngine;
FuelInjector injector 
 
}

They look auwfully similiar and they are, difference is in concept....
as far as litterature states :
Composition is type of aggregation but they are not the same thing conceptualy,
first example states that agregated Object, in that case Car, can exist independently of the Agregator, cars can be outside of garage
and second example states that agregated Object is a part of the whole unit and should not exist without it .this case engine is part of the car, and you can't just buy only engine to drive to work with ...

[Ramaka Naveen]

Hi,
your explaination has cleared my doubts

[mahapatra satya]

thax swati for explaining in simple way.
i had also same doubt as dipti.th a lot.