👁 Object Associations

Composition

final class Company{
private final Employee Employee;
{
 Company(EmpDetails details) {
 engine = new Employee(details);
 }
 void assign() {
 emp.work();
 } 
}

Aggregation

final class Company{
 private Employee engine;
 void addEmployee(Employee emp) {
 this.emp = emp;
 }
 void assign() {
 if (emp != null)
 emp.work();
 }
}

Dependency

final class Company{
 void assign(Employee emp) {
 if (emp != null)
 emp.work();
 }
}

Abstraction

public interface Employee{
 public void work();
 public void off();
 public void quit();
}

Realisation

public abstract class Engineer implements Employee
{
 public void work();
 public void off();
 public void quit();
}

Generalization

public class SWEngineer extends Engineer
{
 public void work()
 {
 System.out.println('SW Engineer working');
 }
 public void off()
 {
 System.out.println('SW Engineer is off today');
 }

 public void quit()
 {
 System.out.println('SW Engineer is quitting');
 }

}

Relationships

UML Relationship Pointers

👁 Image

Resources

• http://leninkumarkoppoju.blogspot.in/2012/10/uml-relations-association-aggregation.html
• http://en.wikipedia.org/wiki/Class_diagram

Reference: Quick Summary : Object Associations from our JCG partner Srividhya Umashanker at the Thoughts of a Techie blog.