package oopsconcepts;

import java.util.ArrayList;

import java.util.List;

class Student {

String name;

int id;

String dept;

Student(String name, int id, String dept) {

this.name = name;

this.id = id;

this.dept = dept;

}

}

class Department {

String name;

private List<Student> students;

Department(String name, List<Student> students) {

this.name = name;

this.students = students;

}

public List<Student> getStudents() {

return students;

}

}

class Institute {

String instituteName;

private List<Department> departments;

Institute(String instituteName, List<Department> departments) {

this.instituteName = instituteName;

this.departments = departments;

}

public int getTotalStudentsInInstitute() {

int noOfStudents = 0;

List<Student> students;

for(Department dept: departments) {

students = dept.getStudents();

for(Student s: students) {

noOfStudents++;

}

}

return noOfStudents;

}

}

public class Aggregation {

public static void main(String[] args) {

Student s1 = new Student("Mia", 1, "CSE");

Student s2 = new Student("Priya", 2, "CSE");

Student s3 = new Student("John", 1, "EE");

Student s4 = new Student("Rahul", 1, "EE");

// Making list of CSE Students

List<Student> cse_students = new ArrayList<Student>();

cse_students.add(s1);

cse_students.add(s2);

// Making List of EE Students

List<Student> ee_students = new ArrayList<Student>();

ee_students.add(s3);

ee_students.add(s4);

Department CSE = new Department("CSE", cse_students);

Department EE = new Department("EE", ee_students);

List<Department> departments = new ArrayList<Department>();

departments.add(CSE);

departments.add(EE);

// creating an instance of Institute.

Institute institute = new Institute("BITS", departments);

System.out.println("Total students in institute are: "+ institute.getTotalStudentsInInstitute());

}

}