has -a relation ship

[Divya Gehlot]

Hi,
I know its a silly topic to post but i am little bit confused with has -a relationship. Can any one help me on this topic and explain me with examples.
Thanks in advance.
Divya
[ July 06, 2007: Message edited by: Divya Gehlot ]

[Chandra Bhatt]

Hi Divya,

Perhaps you may see something like following in the exam:

1- Film and Actor (IS-A relationship) : false
2- Car and Tires (Has-A relationship) : true
3- Bike and Honda (IS-A relationship) : true
etc.

class Car{}
class Employee {
 Car c1 = new Car();
}

Employee HAS-A Car.


Thanks,

[Raghavan Muthu]

Hi Divya,

Has- a relationship comes when you have an instance of one class as a member of another class. Lets Say, you have two classes A and B and you have an instance of B as a member of class A. In that case, class A is said to follow "has-a" relationship with class B.

A live example, a Bathroom class has an instance of Tub class as its member. In such case, "A Bathroom has a tub." Other example would be, "A ClassRoom has a BlackBoard" - where the ClassRoom class is having an instance of BlackBoard class as its instance member.

Whereas, "is-a" relationship speaks its deriving from one other. "An Employee is a Person will hold good but NOT an Employee has a Person". In this case, An employee extends a Person. In other words, An employee is a subclass of a Person class.

Hope this helps.

[Divya Gehlot]

Hi,
First of all thanks for clearing my doubt. what I understood is if we create any refrence variable of a class and implementing in some class then it will be a has a relationship . correct???
Correct me if i am wrong

[Akhilesh Trivedi]

OOP is all about mapping real-world objects and establishing relationships among them. We do it by identifying classes and IS-A, HAS-A relationships.
More often has-a relationship defines composition of the object.

1. An Animal has legs.
2. An Animal has tail.
3. An Animal has ears.

so,

   
class animal
{
 int legs; 
 int tail;
 int ears;
}
public class MainClass
{
 
}

[ July 06, 2007: Message edited by: Akhilesh Trivedi ]

[Akhilesh Trivedi]

What I understood is if we create any refrence variable of a class and implementing in some class then it will be a has a relationship

You are right. But its the other way round, if you have a HAS-A relationship between two classes, only then you will put the reference of one class into another, as a member of that class.

[Divya Gehlot]

Hi,
Thanks I got it