The Difference Between Aggregation and Composition in Object-Oriented Programming
Aggregation vs Composition
Introduction
•
In normal terms, they both refer to member
object but the survival or existence of th
e
member object makes the differences.
Aggregation
•
Aggregation is also known as a 'has a'
relationship because the containing object
has
a
member object and the member object can
survive or exist without the enclosing or
containing class or can have a meaning after
the lifetime of the enclosing object also.
Aggregation Continues
•
Example
:
Room has a table and the table can
exist without the room. The table can have
meaning without the room also.
Aggregation Continues
How to implement Aggregation in
coding
•
How can we manage that?
Implement Aggregation in coding
•
public class Address
{. . .
}
•
public class Person
•
{•
private Address address;
•
public Person(Address address)
•
{•
this.address = address;
•
}
•
. . .
•
}
Implement Aggregation in coding
•
Address address = new Address();
Person person = new Person(address);
•
or
•
Person person = new Person( new Address() );
Composition
•
T
he member object
is a part of
the containing
class and the member object cannot survive
or exist outside the enclosing or containing
class or doesn
’
t have a meaning after the
lifetime of the enclosing object.
Composition Continues
•
Example
:
Computer Science Department is a
part of the College. The Computer Science
Department cannot exist without the college
and the department has no meaning after the
lifetime of the college.
Composition Continues
How to implement Composition in
coding
•
How can we manage that?
Implement Composition in coding
•
public class Engine
{. . .
}
•
public class Car
•
{•
Engine e = new Engine();
•
.......
•
}
Aggregation and Composition are two important concepts in object-oriented programming. Aggregation refers to a 'has-a' relationship where the contained object can survive independently, while Composition indicates that the member object is part of the containing class and cannot exist separately. This guide explores examples and implementation of both concepts in coding.
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Presentation Transcript
Introduction In normal terms, they both refer to member object but the survival or existence of the member object makes the differences.
Aggregation Aggregation is also known as a 'has a' relationship because the containing object has a member object and the member object can survive or exist without the enclosing or containing class or can have a meaning after the lifetime of the enclosing object also.
Aggregation Continues Example: Room has a table and the table can exist without the room. The table can have meaning without the room also.
How to implement Aggregation in coding How can we manage that?
Implement Aggregation in coding public class Address { . . . } public class Person { private Address address; public Person(Address address) { this.address = address; } . . . }
Implement Aggregation in coding Address address = new Address(); Person person = new Person(address); or Person person = new Person( new Address() );
Composition The member object is a part of the containing class and the member object cannot survive or exist outside the enclosing or containing class or doesn t have a meaning after the lifetime of the enclosing object.
Composition Continues Example :Computer Science Department is a part of the College. The Computer Science Department cannot exist without the college and the department has no meaning after the lifetime of the college.
How to implement Composition in coding How can we manage that?
Implement Composition in coding public class Engine { . . . } public class Car { Engine e = new Engine(); ....... }
