In this weekly exercise, you will implement a hierarchy of classes as described

Question

In this weekly exercise, you will implement a hierarchy of classes as described and. utilizing polymorphism, objects of the classes are exercised in a client program. Design a class hierarehy consisting of Publication, Magazine, Book, and Kids Magazine classes as described below. A Publication has a publisher, number of pages, a price, and a title. The class should implement a toString() method that displays all of this information. This class should be abstract. A Magazine is a kind of publication that has a publication unit (monthly, weekly, biweekly). Magazine should have toString() that display all the information. A Book is a kind of publication that has an author. Book should also have toString(). A KidsMagazine is a kind of magazine that has a recommended age range. Again, KidsMagazine should have toString(). Implement a client class that stores 8 different types of publications: magazine, book, or kid's magazine in an array of Publication. Exploit polymorphism and print the information about each object stored in the array.

Explanation / Answer

abstract class Publication //base class
{
    private String publisher;
    private int pages;
    private String title;
  
    public Publication(String publisher,int pages,String title)//argument constructor
    {
        this.publisher = publisher;
        this.pages = pages;
        this.title = title;
    }
  
    public String toString()
    {
        return "Publisher : "+publisher + " Number of pages : "+pages + " Title : "+title;
    }
  
  
}
class Magazine extends Publication //derived class
{
    private String publicationUnit;
  
    public Magazine(String publisher,int pages,String title,String publicationUnit)//argument constructor
    {
        super(publisher,pages,title);// call to base class constructor
        this.publicationUnit = publicationUnit;
    }
  
    public String toString()
    {
        return super.toString() +" Publication Unit : "+publicationUnit;// call super.toString()
    }
}
class Book extends Publication
{
    private String author;
  
    public Book(String publisher,int pages,String title,String author)
    {
        super(publisher,pages,title);
        this.author = author;
    }
  
    public String toString()
    {
        return super.toString() +" Book Author: "+author;
    }
  
}
class KidsMagazine extends Publication
{
    private int age;
  
    public KidsMagazine(String publisher,int pages,String title,int age)
    {
        super(publisher,pages,title);
        this.age = age;
    }
     public String toString()
    {
        return super.toString()+" Kids Magazine Recommended Age : "+age;
    }
  
  
}
class TestPublications
{
   public static void main (String[] args)
   {
       Publication[] publications = new Publication[8];//array of publications
      
       publications[0] = new Book("Paperback",367,"Swing","James Gosling");
      
       publications[1] = new Magazine("BBC",78,"BBC News","daily");
      
       publications[2] = new KidsMagazine("National Geographic",58,"Little Kids",5);
      
       for(int i=0;i<3;i++)
       {
            System.out.println(" Publication "+ (i+1)+" "+ publications[i].toString());
       }
   }
}

Output:

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