Composite design pattern

 Composite design pattern is the part of structural design pattern .

When we need a composite object what will maintain a tree structure then we can use composite design pattern .

let's see an example . We want to develop our company organogram -

Project managers and sales managers works under the CTO.  Developer works under the Project managers. Sales persons works under the sales manager.

public class Employee {

private String name;

private String department;

private int salary;

List<Employee> suborddinates;

public Employee(String name, String department, int salary) {

this.name = name;

this.department = department;

this.salary = salary;

suborddinates = new ArrayList<Employee>();

}

public void addSubordinates(Employee employee) {

suborddinates.add(employee);

}

public List<Employee> getSubordinates() {

return suborddinates;

}

@Override

public String toString() {

return "Employee [name=" + name + ", department=" + department + ", salary=" + salary + "]";

}

} 

//Main class

public class MainApp {

public static void main(String[] args) {

Employee cto = new Employee("msr", "CTO", 100000);

Employee salesManager = new Employee("Hera", "Sales Manager", 80000);

Employee productManager = new Employee("Shahin", "Product Manager", 80000);

Employee sales1 = new Employee("makku", "Sales", 10000);

Employee sales2 = new Employee("Rumana", "Sales", 20000);

Employee dev1 = new Employee("lokman", "Developer", 60000);

Employee dev2 = new Employee("Sahabur", "Developer", 60000);

cto.addSubordinates(productManager);

cto.addSubordinates(salesManager);

productManager.addSubordinates(dev1);

productManager.addSubordinates(dev2);

salesManager.addSubordinates(sales2);

salesManager.addSubordinates(sales1);

System.out.println(cto.toString());

for (Employee manager : cto.getSubordinates()) {

System.out.println(manager.toString());

for (Employee junior : manager.getSubordinates()) {

System.out.println(junior.toString());

}

}

//output

Employee [name=msr, department=CTO, salary=100000]

Employee [name=Shahin, department=Product Manager, salary=80000]

Employee [name=lokman, department=Developer, salary=60000]

Employee [name=Sahabur, department=Developer, salary=60000]

Employee [name=Hera, department=Sales Manager, salary=80000]

Employee [name=Rumana, department=Sales, salary=20000]

Employee [name=makku, department=Sales, salary=10000]