Aggregation in Java
Describe Aggregation in Java
If a class contains another class or object of another class as its member then HAS-A relation is created between their class and their objects.
Aggregation represents part and whole relation between classes. It is weaker relation as both entity can exist independently.
For eg: Room has chairs, Room has tables.
Aggregation can be implemented by containing the object of a class as member of another class.
Lets take an example of Employee and Address classes to implement aggregation.
Here Address class object is a data member in Employee class.
JbkAddress.java
package com.javabykiran.aggregation;
public class JbkAddress {
public String city;
public String zipcode;
public JbkAddress(String city, String zipcode) {
super();
this.city = city;
this.zipcode = zipcode;
}
}
JbkEmployee.java
package com.javabykiran.aggregation;
public class JbkEmployee {
public int id;
public String name;
public JbkAddress address;
public JbkEmployee(int id, String name, JbkAddress address) {
super();
this.id = id;
this.name = name;
this.address = address;
}
public void display() {
System.out.println("Id -> " + id);
System.out.println("Name -> " + name);
System.out.println("City -> " + address.city);
System.out.println("zipcode -> " + address.zipcode);
}
}
JbkAggregationTest.java
package com.javabykiran.aggregation;
public class JbkAggregationTest {
public static void main(String[] args) {
JbkAddress jbkaddress = new JbkAddress("Pune", "411052");
JbkEmployee jbkemployee = new JbkEmployee(1, "JavaBYKiran", jbkaddress);
jbkemployee.display();
}
}
Output:
Id -> 1
Name -> JavaBYKiran
City -> Pune
zipcode -> 411052