public class Animal{}

public class Dog extends Animal{}

public interface UserService{}

public class UserServiceImpl implements UserService{}

public class Train{

public void move(){}

}

public class Person{

public void move(Train train){

train.move();

}

}

public class Car{}

public class Person{

private Car car;

publicvoid setCar(Car car){

this.car=car;

}

}

public class Engine{}

public class Car{

private Engine engine;

public Car(Engine engine){

this.engine=engine;

}

}

public class Brain{}

public class Person{

private Brain brain;

public Person(){

this.brain=new Brain();

}

}

// Java program to illustrate the

// concept of Association

import java.io.*; 

// class bank

class Bank

{

    private String name; 

    // bank name

    Bank(String name)

    {

        this.name = name;

    } 

    public String getBankName()

    {

        return this.name;

    }

}  

// employee class

class Employee

{

    private String name; 

    // employee name

    Employee(String name)

    {

        this.name = name;

    } 

    public String getEmployeeName()

    {

        return this.name;

    }

} 

// Association between both the

// classes in main method

class Association

{

    public static void main (String[] args)

    {

        Bank bank = new Bank("Axis");

        Employee emp = new Employee("Neha"); 

        System.out.println(emp.getEmployeeName() +

               " is employee of " + bank.getBankName());

    }

} 

// Java program to illustrate

//the concept of Aggregation.

import java.io.*;

import java.util.*;

// student class

class Student

{

String name;

int id ;

String dept;

Student(String name, int id, String dept)

{

this.name = name;

this.id = id;

this.dept = dept;

}

}

/* Department class contains list of student

Objects. It is associated with student

class through its Object(s). */

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;

}

}

/* Institute class contains list of Department

Objects. It is asoociated with Department

class through its Object(s).*/

class Institute

{

String instituteName;

private List<Department> departments;

Institute(String instituteName, List<Department> departments)

{

this.instituteName = instituteName;

this.departments = departments;

}

// count total students of all departments

// in a given institute

public int getTotalStudentsInInstitute()

{

int noOfStudents = 0;

List<Student> students;

for(Department dept : departments)

{

students = dept.getStudents();

for(Student s : students)

{

noOfStudents++;

}

}

return noOfStudents;

}

} 

// main method

class GFG

{

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", 2, "EE");

// making a List of

// CSE Students.

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

cse_students.add(s1);

cse_students.add(s2);

// making a 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.print("Total students in institute: ");

System.out.print(institute.getTotalStudentsInInstitute());

}

}

// Java program to illustrate

// the concept of Composition

import java.io.*;

import java.util.*;

// class book

class Book

{

public String title;

public String author;

Book(String title, String author)

{

this.title = title;

this.author = author;

}

}

// Libary class contains

// list of books.

class Library

{

// reference to refer to list of books.

private final List<Book> books;

Library (List<Book> books)

{

this.books = books;

}

public List<Book> getTotalBooksInLibrary(){

return books;

}

}

// main method

class GFG

{

public static void main (String[] args)

{

// Creating the Objects of Book class.

Book b1 = new Book("EffectiveJ Java", "Joshua Bloch");

Book b2 = new Book("Thinking in Java", "Bruce Eckel");

Book b3 = new Book("Java: The Complete Reference", "Herbert Schildt");

// Creating the list which contains the

// no. of books.

List<Book> books = new ArrayList<Book>();

books.add(b1);

books.add(b2);

books.add(b3);

Library library = new Library(books);

List<Book> bks = library.getTotalBooksInLibrary();

for(Book bk : bks){

System.out.println("Title : " + bk.title + " and "

+" Author : " + bk.author);

}

}

}

// Java program to illustrate the

// difference between Aggregation

// Composition.

import java.io.*;

// Engine class which will

// be used by car. so 'Car'

// class will have a field

// of Engine type.

class Engine

{

// starting an engine.

public void work()

{

System.out.println("Engine of car has been started ");

}

}

// Engine class

final class Car

{

// For a car to move,

// it need to have a engine.

private final Engine engine; // Composition

//private Engine engine; // Aggregation

Car(Engine engine)

{

this.engine = engine;

}

// car start moving by starting engine

public void move()

{

//if(engine != null)

{

engine.work();

System.out.println("Car is moving ");

}

}

}

class GFG

{

public static void main (String[] args)

{

// making an engine by creating

// an instance of Engine class.

Engine engine = new Engine();

// Making a car with engine.

// so we are passing a engine

// instance as an argument while

// creating instace of Car.

Car car = new Car(engine);

car.move();

}

}