Composite design pattern is a type of structural design pattern and is used when you want to treat group of similar objects as one.
This pattern creates a class containing group of its own objects. This class provides ways to modify its group of same objects
Example: Employee Hierarchy of an organisation
Employee.java
package Patterns.Structural.composite; import java.util.ArrayList; import java.util.List; public class Employee { private String name; private String department; private String id; private List<Employee> subOrdinates; public Employee(String name, String department, String id) { this.name = name; this.department = department; this.id = id; this.subOrdinates = new ArrayList<>(); } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getDepartment() { return department; } public void setDepartment(String department) { this.department = department; } public String getId() { return id; } public void setId(String id) { this.id = id; } public List<Employee> getSubOrdinates() { return subOrdinates; } public void addSubordinates(Employee e) { this.subOrdinates.add(e); } @Override public String toString() { return "Employee [name=" + name + ", department=" + department + ", id=" + id+"]"; } } Main.java
package Patterns.Structural.composite; public class OrganizationMain { public static void main(String args[]){ //creating different employees like ceo,ed(executive director),vp and sde's Employee ceo = new Employee("Dishant Patil", "CEO", "1"); Employee ed1 = new Employee("Sushma Mishra", "Head Markets", "2"); Employee vp1 = new Employee("Alok Mishra", "Markets", "3"); Employee vp2 = new Employee("Dishant Patil", "Markets", "4"); Employee ed2 = new Employee("Asutosh Dwivedi", "Head Credits", "5"); Employee vp3 = new Employee("Arunodaya Pandey", "Credits", "6"); Employee sde1 = new Employee("Prashant Mishra", "Markets", "7"); Employee sde2 = new Employee("Sandeep Padhi", "Credits", "8"); //updating subordinates based on department type //ed's reporting to ceo ceo.addSubordinates(ed1); ceo.addSubordinates(ed2); //vp's reporting to their respective ed's ed1.addSubordinates(vp1); ed1.addSubordinates(vp2); ed2.addSubordinates(vp3); //sde's reporting to vp's vp1.addSubordinates(sde1); vp1.addSubordinates(sde2); //printing the hierarchy System.out.println(ceo); for(Employee e : ceo.getSubOrdinates()){ System.out.println(e); for(Employee subordinate : e.getSubOrdinates()){ System.out.println(subordinate); } } } } Output
Employee [name=Dishant Patil, department=CEO, id=1] Employee [name=Sushma Mishra, department=Head Markets, id=2] Employee [name=Alok Mishra, department=Markets, id=3] Employee [name=Dishant Patil, department=Markets, id=4] Employee [name=Asutosh Dwivedi, department=Head Credits, id=5] Employee [name=Arunodaya Pandey, department=Credits, id=6] 
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