Chapter 9.4, Problem 18SCP

Explanation of Solution

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...

Explanation of Solution

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...