What is Aggregation in java with example

Aggregation is a relationship between two class like association. It is represents as Has-A relationship.

For example we take two class which name is company class and employee class.

For Example:-

Create a class which name is AggregationCompanyClass.java

/**

 *

 * @author pradeep

 */

class AggregationCompanyClass

{

   int JobId;

   String Name;

   String MobNumber;

   AggregationCompanyClass(int jobId, String name, String mobnumber)

   {

       this.JobId=jobId;

       this.Name =name;

       this.MobNumber = mobnumber;

   }

}

class EmployeeClass

{

   int EmpId;

   String EmpName;

   AggregationCompanyClass EmpAddr; 

   EmployeeClass(int id, String name, AggregationCompanyClass addr){

       this.EmpId=id;

       this.EmpName=name;

       this.EmpAddr = addr;

   }

   public static void main(String args[]){

       AggregationCompanyClass addrs = new AggregationCompanyClass(9897357, “HCL”, “8000909997”);

       EmployeeClass empObj = new EmployeeClass(371, “Monty”, addrs);

       System.out.println(empObj.EmpId);

       System.out.println(empObj.EmpName);

       System.out.println(empObj.EmpAddr.JobId);

       System.out.println(empObj.EmpAddr.Name);

       System.out.println(empObj.EmpAddr.MobNumber);

   }

}

Result : Output of this program is

run:

371

Monty

9897357

HCL

8000909997

BUILD SUCCESSFUL

Note : Aggregation is use to maintain code re-usability.