Bookstore program

Question

I am writing a bookstore type program with a data class and an executable class. My problem is, when I display the array with all 6 books, it displays 6 lines of the same book. I am not exactly sure what I did wrong.

Here are the instructions I was given:

Class TestBook

This class needs a main method and two more methods.

In main:

create an array capable of holding six Book objects.

use the parameterized constructor to specify the data in the first four elements of this array

use the no-arg constructor to create the two remaining books in the array.

process the array with a foreach loop to display the array at this point.

call the finishArray() method with the array as the only argument.

call the reduceBooks() method with the array as the sole argument.

repeat the code needed by Step 4 above.

display the most expensive book after the discounts.

In finishArray():

this is a void method.

use the setter methods to specify the data in all fields of the last two books in the array.

In reduceBooks():

this method returns a Book instance.

use a loop (any type) to reduce the price of every book in the array by 40%.

determine the most expensive book after the discounts and return this book to main.

Here is my code:

package week6.yedkois;


public class TestBook {
        private static String _title;
        private static String _author;
        private static int _pages;
    private static double _price;

    public TestBook(String title, String author, int pages, int price){
        this._title = title;
        this._author = author;
        this._pages = pages;
        this._price = price;

    }

    public static void main(String[] args){

        Book[] books = new Book[6];

        Book book1 = new Book("Java Programming", "Liang", 1320, 149.99);
        Book book2 = new Book("Rainbow Six", "Tom Clancy", 350, 10.99);
        Book book3 = new Book("Tangerine", "Bloor", 180, 8.99);
        Book book4 = new Book("End of Watch", "King", 320, 21.42);
        Book book5 = new Book();
        Book book6 = new Book();


        books[0] = book1;
        books[1] = book2;
        books[2] = book3;
        books[3] = book4;
        books[4] = book5;
        books[5] = book6;

        for (Book u : books)
            System.out.print(u);


    }

    public TestBook(){
        Book[] books = new Book[6];
        Book book5 = new Book("House", "House", 1320, 89);
        Book book6 = new Book("Car", "Car", 1320, 89);



    }   

    public static double reduceBooks(Book[] books){


        return 0;

    }

    void finishArray(){
    Book newbook = new Book();
    newbook.setTitle(_title);
    newbook.setAuthor(_author);
    newbook.setPages(_pages);
    newbook.setPrice(_price);

    }   
}

here is the data class

package week6.yedkois;

public class Book {

    private static String _title;
    private static String _author;
    private static int _pages;
    private static double _price;
    public static int numBooks = 0;
    public  Book(){
        for (int i = 0; i > 6; i++)
            numBooks++;

    }

    public Book(String title, String author, int pages, double price)
    {   super();
        this._title = title;
        this._author = author;
        this._pages = pages;
        this._price = price;
    }

    public String getTitle()

    {
        return _title;
    }

    public void setTitle(String title)

    {
        this._title = title;
    }

    public String getAuthor()

    {
        return _author;
    }

    public void setAuthor(String author)

    {
        this._author = author;
    }

    public int getPages()

    {
        return _pages;
    }

    public void setPages(int pages)

    {
        this._pages = pages;
    }

    public double getPrice()

    {
        return _price;
    }

    public void setPrice(double price)

    {
        this._price = price;

    }

    public String toString()
    {
        return "Book [Title: " + _title + ", Author: " + _author + ", Pages: " + _pages + ", Price: $" + _price +"]\n";
    }
}

I guess that you will a `Book` `toString` method, also get rid of `static` modifier — Scary Wombat, Feb 20 '17 at 02:38
see http://stackoverflow.com/questions/413898/what-does-the-static-keyword-do-in-a-class — Scary Wombat, Feb 20 '17 at 02:40

score 1 · Answer 1 · answered Feb 20 '17 at 03:31

your problem is that, you set instance variables as static variable on your book class

public class Book {

    private static String _title;
    private static String _author;
    private static int _pages;
    private static double _price;

    public static int numBooks = 0;

a static variable, will be shared among all instances of you class book. so, following your current code, every time you create a new instance, you will replace its values and make them available for all your instances.

to solve your issue, just delete the word static on these local variables and you are good to go.

public class Book {

    private String _title;
    private String _author;
    private int _pages;
    private double _price;

    public int numBooks = 0;

Bookstore program

1 Answers1