Structural Design Pattern: Composite Pattern

The Composite Pattern states that clients should be able to interact with items, regardless of whether these objects form a hierarchy of objects or not, in a generic manner.

The advantage of using the Composite Design Pattern is that it allows for the creation of complex hierarchical structures by treating individual objects and groups of objects uniformly.

• It establishes class hierarchies that include both basic and intricate things. 
• It facilitates the addition of new types of components. 
• It has the advantage of having a flexible structure with easily controllable classes or interfaces.

Source code of Employee.java

package com.t4b.test.java.dp.sp.cp; import java.util.ArrayList; import java.util.List; class Employee { private String name; private String designation; private List<Employee> subordinates; public Employee(String name, String designation) { this.name = name; this.designation = designation; subordinates = new ArrayList<Employee>(); } public void addSubordinate(Employee e) { subordinates.add(e); } public void removeSubordinate(Employee e) { subordinates.remove(e); } public List<Employee> getSubordinates() { return subordinates; } @Override public String toString() { return "Employee [name=" + name + ", designation=" + designation + ", subordinates=" + subordinates + "]"; } }

Source code of TestMain.java

package com.t4b.test.java.dp.sp.cp; public class TestMain { public static void main(String[] args) { Employee ceo = new Employee("Smith", "CEO"); Employee salesHead = new Employee("Johnson", "Sales"); Employee marketingHead = new Employee("Williams", "Marketing"); ceo.addSubordinate(salesHead); ceo.addSubordinate(marketingHead); Employee programmer = new Employee("Jones", "Programmer"); marketingHead.addSubordinate(programmer); programmer = new Employee("Brown", "Programmer"); marketingHead.addSubordinate(programmer); Employee tester = new Employee("Davis", "Tester"); salesHead.addSubordinate(tester); tester = new Employee("Miller", "Tester"); salesHead.addSubordinate(tester); System.out.println(ceo); for (Employee e : ceo.getSubordinates()) { System.out.println(e); for (Employee employee : e.getSubordinates()) { System.out.println(employee); } } } }

Happy Exploring!