Compostion
We refer association between two objects as composition, when one class owns other class and other class can not meaningfully exist, when it's owner destroyed, for example Human class is composition of several body parts including Hand, Leg and Heart. When human object dies, all it's body part ceased to exist meaningfully, this is one example of Composition. Another example of Composition is Car and it's part e.g. engines, wheels etc. Individual parts of car can not function, when car is destroyed. While in case of Aggregation, including object can exists without being part of main object e.g. a Player which is part of a Team, can exists without team and can become part of other teams as well. Another example of Aggregation is Student in School class, when School closed, Student still exist and then can join another School or so. In UML notation, composition is denoted by a filled diamond, while aggregation is denoted by an empty diamond, which shows their obvious difference in terms of strength of relationship. Composition is more stronger than Aggregation. In Short, relationship between two objects is referred as association, and an association is known as composition when one object owns other, while an association is known as aggregation when one object usesother object.
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbzDRNCY
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbyrMqzS
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbwmlh5G
Relationships
Relationships provide a pathway for communication between objects
If two objects need to communicate, there should be a link between the two.
Three types of relationships are:
We refer association between two objects as composition, when one class owns other class and other class can not meaningfully exist, when it's owner destroyed, for example Human class is composition of several body parts including Hand, Leg and Heart. When human object dies, all it's body part ceased to exist meaningfully, this is one example of Composition. Another example of Composition is Car and it's part e.g. engines, wheels etc. Individual parts of car can not function, when car is destroyed. While in case of Aggregation, including object can exists without being part of main object e.g. a Player which is part of a Team, can exists without team and can become part of other teams as well. Another example of Aggregation is Student in School class, when School closed, Student still exist and then can join another School or so. In UML notation, composition is denoted by a filled diamond, while aggregation is denoted by an empty diamond, which shows their obvious difference in terms of strength of relationship. Composition is more stronger than Aggregation. In Short, relationship between two objects is referred as association, and an association is known as composition when one object owns other, while an association is known as aggregation when one object usesother object.
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbzDRNCY
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbyrMqzS
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbwmlh5G
Three types of relationships are:
An association is a bi-directional connection between classes
An association is shown as a line connecting the related classes
An Aggregation / Composition is a stronger form of relationship where the relationship is between a whole and its parts
An Aggregation is shown as a line connecting the related classes with an unfilled diamond next to the class representing the whole. For Composition, the dialog will be filled.
A dependency relationship is a weaker form of relationship showing a relationship between a client and a supplier where the client does not have semantic knowledge of the supplier
A dependency is shown as a dashed line pointing from the client to the supplier
An association is shown as a line connecting the related classes
An Aggregation / Composition is a stronger form of relationship where the relationship is between a whole and its parts
An Aggregation is shown as a line connecting the related classes with an unfilled diamond next to the class representing the whole. For Composition, the dialog will be filled.
A dependency relationship is a weaker form of relationship showing a relationship between a client and a supplier where the client does not have semantic knowledge of the supplier
A dependency is shown as a dashed line pointing from the client to the supplier
Read more: http://javarevisited.blogspot.com/2014/02/ifference-between-association-vs-composition-vs-aggregation.html#ixzz3kbwRL6lt
Relationships
Association | Defines a relationship between classes. Compositon and Aggregation are types of associations |
Composition | the Employee is encapsulated within the Company . There is no way for the outside world to get a reference to the Employee. The Employee is created and destroyed with the company |
Aggregation | The Company also performs its functions through an Employee, but the Employee is not always an internal part of the Company . Employees can be exchanged, or even completely removed. As the employee is injected, the Employee reference can live outside the Company. |
Dependency | The company does not hold the employee reference. It receives an employee reference only to the scope an operation. Company is dependent on the Employee object to perform an operation |
Abstraction | Defines the basic operations the implementer should adher to. Employee interface lists the general behavior of an employee |
Realization | A class implements the behavior defined by the other other class or interface |
Generalization | A class which is a special form of a parent class |
Generalization
Realisation
Abstraction
Dependency
Composition
Aggregation
Composition : Since Engine is part-of Car, relationship between them is Composition. Here is how they are implemented between Java classes.
Aggregation : Since Organization has Person as employees, relationship between them is Aggregation. Here is how they look like in terms of Java classes
public class Car {
//final will make sure engine is initialized private final Engine engine; public Car(){ engine = new Engine(); } } class Engine { private String type; }
Aggregation : Since Organization has Person as employees, relationship between them is Aggregation. Here is how they look like in terms of Java classes
public class Organization {
private List employees;
}
public class Person {
private String name;
}