A publishing has a publishing, number of pages, a price, an owner, and a title.

Question

A publishing has a publishing, number of pages, a price, an owner, and a title. When
a publication object is created using a constructor the number of pages , price, and
The title must be supplied. A default constructor uses blank and zero values. When
a publication is created, it no owner. An owner can be set, and the publication explicitly sold, using The:
Double sell(String owner, double amount)
Method. The method call
p.sell(String owner, double amount)
sells publication p to owner and returns the change, from amount if there is any . For example, if the price of publication p is $ 5.89, then p.sell(“shai”, 6.0); sets “shai” as the owner of publication p and return 0.11. The sell(…) method can be called numerous times, as the publication is sold and resold.

Explanation / Answer

I sent you a PM for clarification, don't you if you missed that or...

I'm not sure if a class publishing containing an object of type publishing in it represents a good example of composition, I don't know. I may be reading the requirements wrong, or there's a typo somewhere, or some already existing classes and/or context needs to be included here.
Anyway, I'll go ahead and do what makes sense to me, without composition, and then you can explain what's missing/wrong and we can edit it later.

--------------------------------------------------------------------------------
the class Publishing.java

public class Publishing {
   
    /* Private variables declaration */
    private int pages;
    private double price;
    private String title;
    private String owner;
   
    /* Constructors */
    public Publishing()
    {
        pages = 0;
        price = 0;
        title = "";
        owner = "";
    }
    public Publishing(int pgs, double pr, String titl )
    {
        pages = pgs;
        price = pr;
        title = titl;
        owner = "";
    }
   
    /* sell method implemented */
    public double sell(String own, double amount)
    {
        owner = own;
        return amount - price;
    }
   
    /* toString method just to display stuff */
    public String toString()
    {
        return title + " pages: " + pages +
                " price: " + price +
                " owner: " + owner;
    }
   
}

--------------------------------------------------------------------------------
the test class for it PublishingTest.java

public class PublishingTest {

    public static void main(String[] args) {
       
        System.out.println("Initialzing a publication");
        Publishing p = new Publishing(120, 5.89, "An Interesting Read");
        System.out.println(p.toString());
        System.out.println("Selling it to Shai, change for $6.00...");
        double change = p.sell("Shai", 6);
        System.out.println("Sold! Change is: " + change);
        System.out.println(p.toString());
    }
}

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