Difference between "is-a" and "has-a" relationship:

"is-a" relationship "has-a" relationship

It is a static binding. It is a dynamic binding.

Inheritance follows "is-a" relationship...

Creating has-a relationship in program code:

• Composition is defined with "has-a" relationship.
• Composition is a form of aggregation.
• In "has-a" relationship, instance variables are used as references to other objects.
• Both entities are highly dependent on each other in composition.
• It is also known as "part-of" relationship.
• In composition, no one entity cannot exists without other entity.

Example code for "has-a" relationship:

File name "Book.java"

/Import package

import java.io.*;

//Create a class

class Book

{

//Declare the variable

public String book_name;

//Define the constructor

Book(String book_name)

{

//Set the value

this.book_name = book_name;

}

}

File name: "Library.java"

import java.util.List;

class Library

{

//Make a reference of Book to refer the list of books

private final List<Book> bks;

//Define the constructor that refers the object

Library (List<Book> book)

{

//Assign one object to other

this.bks = book;

}

//Define the method

public List<Book> getTotalBooks()

{

//Return the list of books

return bks;

}

}

File name: "LibraryMain.java"

//Import the package

import java.io.*;

import java.util.*;

//create a class

class LibraryMain

{

//Define the main() method

public static void main(String[] args)

{

// Create objects of Book class...