Instantiating an Object of a Class Confusion

[mariejt]

Good Morning!

I am trying to create a Book2 object and assign to Inventory_Program6a. When I try the following: Book2 newBookTitle = Book2();

I get the error message:
C:\java>javac Inventory_Program6a.java
Inventory_Program6a.java:325: cannot find symbol
symbol : constructor Book2()
location: class Book2
Book2 newBookTitle = new Book2();
^
1 error

I can't for the life of me figure out why I can't create a Book2 object.

Any assistance is greatly appreciated!

I've attached my code for both Inventory_Program6a and Book2

Inventory_Program6a:
import java.awt.*;
import java.io.*;
import java.text.*;
import java.util.*;
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import javax.swing.JLabel;

public class Inventory_Program6a extends JFrame
{
	// instance variables
	private int displayBooks = 0; // variable for actionEvents
	private int arrayCount;

	private JButton firstButton;
	private JButton previousButton;
	private JButton nextButton;
	private JButton lastButton;
	private JButton addButton;
	private JButton deleteButton;
	private JButton modifyButton;
	private JButton saveButton;
	private JButton searchButton;

	private JTextField bookTitleField;
	private JTextField itemNumberField;
	private JTextField unitsInStockField;
	private JTextField bookPriceField;
	private JTextField inventoryValueField;
	private JTextField bookAuthorField;
	private JTextField restockingFeeField;

	private JLabel bookTitleLabel;
	private JLabel itemNumberLabel;
	private JLabel unitsInStockLabel;
	private JLabel bookPriceLabel;
	private JLabel inventoryValueLabel;
	private JLabel bookAuthorLabel;
	private JLabel restockingFeeLabel;

	private JPanel display;
	private JPanel content;
	private JTextArea textArea;
	private JLabel label;

	// Declare an array of classes
	
	private Book2 myBook[];

	// method to sort inventory by book title
	public Book2[] sortBookInventory()
    	{
        	for(int i = 0; i < myBook.length; i++) 
		{
            	String bookTitle1 = myBook[i].getBookTitle();
            	int min = i;
            	String bookTitle = bookTitle1;
            		for(int j = i+1; j < myBook.length; j++) 
			{
                	String bookTitle2 = myBook[j].getBookTitle();
                		if(bookTitle2.compareTo(bookTitle) < 0) 
				{
                    		min = j;
                    		bookTitle = bookTitle2;
                		}
            		}
            	if(!bookTitle.equals(bookTitle1)) 
		{
                	Book2 temp = myBook[i];
                	myBook[i] = myBook[min];
                	myBook[min] = temp;
           	}
        	}
        		return myBook;
	} // end method sortBookInventory

	// constructor
	public Inventory_Program6a()
	{		
		double totalInventoryValue = 0.0;

		// Specify how many items are in the array
		// instantiate Book2 object
		myBook = new Book2[5];
		myBook[0] = new Book2("The Key Triology", 1, 25, 7.99, "Nora Roberts");
		myBook[1] = new Book2("The Shinning", 2, 15, 5.99, "Stephen King");
		myBook[2] = new Book2("Wild Acre", 3, 7, 4.99, "Phillipa Gregory");
		myBook[3] = new Book2("Dark Paradise", 4, 2, 12.99, "Tami Hoag");
		myBook[4] = new Book2("Dollhouse Murders", 5, 18, 2.95, "Betty Ren Wright");
			
		// call method sort book inventory for display
		sortBookInventory();

		for (int i = 0; i<5; i++)
		{

			// display the book title
			System.out.println("The book title is: " + myBook[i].getBookTitle());

			// display the item number
			System.out.println("The item number is: " + myBook[i].getItemNumber());

			// display the number of units in stock
			System.out.println("The number of units in stock is: " + myBook[i].getBookUnits());

			// display the price per book
			System.out.printf("The price of the book is: $%.2f\n", myBook[i].getBookPrice());

			// display the value of the inventory
			System.out.printf("The value of the inventory is: $%.2f\n", myBook[i].inventoryValue());

			// display the book author
			System.out.println("The book author is: " + myBook[i].getBookAuthor());

			// display the restocking fee
			System.out.println("Restock Fee: " + myBook[i].inventoryValue() * 0.05);

			// calculate total inventory value with restocking fee added
			totalInventoryValue += (myBook[i].inventoryValue() * 1.05);

			// insert blank line
			System.out.println();

		} // end for

		// display the total value of the inventory with the restocking fee
		System.out.printf("The total value of the book inventory including the restocking fee is: $%5.2f.\n", totalInventoryValue);

		// display the total value of the inventory excluding the restocking fee
		System.out.println("The total value of the book inventory is: " + totalInventoryValue());

		//JLabel constructor for logo
		Icon logo = new ImageIcon("C:/book.jpg");
		label = new JLabel(logo);
		label.setToolTipText("Joyce's Logo");

		// create textArea
		textArea = new JTextArea(myBook[3]+"\n");
		
		// Create content panel, set layout
		content = new JPanel();
		content.setLayout(new FlowLayout());
		content.setLayout(new GridLayout(3,4));

		// create JPanel for array items
		display = new JPanel();
		display.setLayout(new FlowLayout());
		display.setLayout(new GridLayout(7,1));

		arrayCount = displayBooks;

		// set window (JFrame) characteristics
		setLayout(new BorderLayout());
		getContentPane().add(new JScrollPane(display), BorderLayout.CENTER);
		getContentPane().add(content, BorderLayout.SOUTH);
		getContentPane().add(label, BorderLayout.NORTH);
		pack();
		setTitle("Book Inventory Program");
		setSize(400, 400); // set frame size
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setLocationRelativeTo(null);

		// initialize components
		
		bookTitleField = new JTextField();
		bookTitleField.setEditable(false);

		itemNumberField = new JTextField();
		itemNumberField.setEditable(false);
	
		unitsInStockField = new JTextField();
		unitsInStockField.setEditable(false);

		bookPriceField = new JTextField();
		bookPriceField.setEditable(false);

		inventoryValueField = new JTextField();
		inventoryValueField.setEditable(false);

		bookAuthorField = new JTextField();
		bookAuthorField.setEditable(false);				

		restockingFeeField = new JTextField();
		restockingFeeField.setEditable(false);	
		
		// initialize components
		firstButton = new JButton("First");
		content.add(firstButton);

		previousButton = new JButton("Previous");
		content.add(previousButton);

		nextButton = new JButton("Next");
		content.add(nextButton);

		lastButton = new JButton("Last");
		content.add(lastButton);

		addButton = new JButton("Add");
		content.add(addButton);

		deleteButton = new JButton("Delete");
		content.add(deleteButton);

		modifyButton = new JButton("Modify");
		content.add(modifyButton);

		saveButton = new JButton("Save");
		content.add(saveButton);

		searchButton = new JButton("Search");
		content.add(searchButton);

		// display JLabels and JTextFields on display panel
		display.add(new JLabel("Book Title: "));
		display.add(bookTitleField);

		display.add(new JLabel("Item Number: "));
		display.add(itemNumberField);

		display.add(new JLabel("Units in Stock: "));
		display.add(unitsInStockField);

		display.add(new JLabel("Book Price: "));
		display.add(bookPriceField);

		display.add(new JLabel("Inventory Value: "));
		display.add(inventoryValueField);
	
		display.add(new JLabel("Book Author: "));
		display.add(bookAuthorField);
	
		display.add(new JLabel("Restocking Fee: "));
		display.add(restockingFeeField);

		// assign actionListener and actionEvent to firstButton
		firstButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
			if (event.getActionCommand()== "First")
			{
			displayBooks = 0;
			}
		setTextFields();
		} // end firstButton actionEvent
		}); // end lastButton actionListener

		// assign actionListener and actionEvent to previousButton
		previousButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
		if (event.getActionCommand()== "Previous")
		displayBooks--;
		if (displayBooks < 0)
		{
		displayBooks = 0;
			if (displayBooks == 0)
			{
			displayBooks = displayBooks = myBook.length-1;
			}
		}
		setTextFields();
		} // end previousButton actionEvent
		}); // end previousBUtton actionListener

		// assign actionListener and actionEvent to nextButton
		nextButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
		if (event.getActionCommand()== "Next")
		displayBooks++;
		if (displayBooks >= myBook.length)
		{
		displayBooks = myBook.length-1;
			if (displayBooks == myBook.length-1)
			{
			displayBooks = 0;
			}
		}
		setTextFields();
		} // end nextButton actionEvent
		}); // end nextButton actionListener

		// assign actionListener and actionEvent to lastButton
		lastButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
		if (event.getActionCommand()== "Last")
		{
		displayBooks = myBook.length-1;
		}
		setTextFields();
		} // end lastButton actionEvent
		}); // end lastButton actionListener

		
		// assign actionListener and actionEvent to lastButton
		addButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
		
		Book2 newBookTitle = new Book2();
		newBookTitle.setBookTitle(bookTitleField.getText());
		} // end addButton actionEvent
		}); // end addButton actionListener




		// assign actionListener and actionEvent to saveButton
		saveButton.addActionListener(new ActionListener()
		{
		public void actionPerformed(ActionEvent event)
		{
		if (event.getActionCommand()== "Save")
		{
			FileOutputStream out;
			PrintStream p;
			try
			{
				String strDirectory = "c:/data";
				new File(strDirectory).mkdir();
				out = new FileOutputStream ("C:/data/inventory.dat");
				p = new PrintStream(out);
					for (int i = 0; i<= 5 - 1; i++)
					{
						p.println("Book Title: " + myBook[i].getBookTitle()+"\n");
						p.println("Item Number: " + myBook[i].getItemNumber()+"\n");
						p.println("Book Units: " + myBook[i].getBookUnits()+"\n");
						p.println("Book Price: " + myBook[i].getBookPrice()+"\n");
						p.println("Inventory Value: " + myBook[i].inventoryValue()+"\n");
						p.println("Book Restocking Fee: " + myBook[i].bookRestockingFee()+"\n");
						p.println("");
					}
				p.close();
				}
			catch (Exception e)
			{
				System.out.println("error");
			}
			}
			setTextFields();

		} // end lastButton actionEvent
		}); // end lastButton actionListener

	} // end constructor

	// method to calculate the value of the entire inventory
	public double totalInventoryValue()
	{ 
		double totalInventoryValue = 0.00;

		for ( int counter = 0; counter < myBook.length; counter++ )

			totalInventoryValue += myBook[counter].inventoryValue();

		return totalInventoryValue;

	} // end method totalBookValue

	// method to setTextFields
	private void setTextFields()
	{
	if (displayBooks == arrayCount)
		{
			displayBooks = 0;
		}
		if (displayBooks < 0)
		{
			displayBooks = arrayCount -1;
		}
	bookTitleField.setText(myBook[displayBooks].getBookTitle()+"\n");
	itemNumberField.setText(myBook[displayBooks].getItemNumber()+"\n");
	unitsInStockField.setText(myBook[displayBooks].getBookUnits()+"\n");
	bookPriceField.setText(myBook[displayBooks].getBookPrice()+"\n");
	inventoryValueField.setText(myBook[displayBooks].inventoryValue()+"\n");
	bookAuthorField.setText(myBook[displayBooks].getBookAuthor()+"\n");
	restockingFeeField.setText(myBook[displayBooks].bookRestockingFee()+"\n");
	} // end method setTextFields

	// main method begins execution of Java application
	public static void main( String args [])
	{ 
		new Inventory_Program6a();
		//create JFrame
		Inventory_Program6a inventory = new Inventory_Program6a();
		inventory.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		inventory.setVisible(true);		
		
	} // end method main

} // end class Inventory_Program6a

Book2:

public class Book2 extends Book
{

	// Book2 variable
	private String bookAuthor; // Author of the book
	

	// Book2 constructor
	public Book2(String bookTitle, int itemNumber, int bookUnits, double bookPrice, String bookAuthor)
	{

		// call super class constructor
		super(bookTitle, itemNumber, bookUnits, bookPrice);
		
		this.bookAuthor = bookAuthor; // initializes bookTitle for Book2
	} // end constructor

	// method to set the book author
	public void setBookAuthor (String bookAuthor)
	{
		this.bookAuthor = bookAuthor;
	} // end method setBookAuthor

	// method to retrieve the book author
	public String getBookAuthor()
	{
		return bookAuthor;
	} // end method getBookAuthor

	// Calculate the stock value
	// Returns the total value of books in stock, adding a 5% restocking fee
	public double inventoryValue()
	{
		return (super.inventoryValue() * 1.05);
	}

	// method for returning the book restocking fee
	public double bookRestockingFee()
	{
		return(super.inventoryValue() * 0.05);
	}

	public String toString()
	{
	return String.format("Book Title: %s\nItem Number: %d\nUnits in Stock: %d\nBook Price: $%.2f\nInventory Value: $%.2f\nBook Author: %s\nRestocking Fee: $%.2f\n", getBookTitle(), getItemNumber(), getBookUnits(), getBookPrice(), inventoryValue(), getBookAuthor(), bookRestockingFee());
	}

} // end class Book2

[cms271828]

Hmmm, I don't get it

In your Book2 class, you've got:

super(bookTitle, itemNumber, bookUnits, bookPrice);

but when I look at java.awt.print.Book,
the only constructor I see is Book().

I've never even seen this class before, but still, if the constructor you are invoking doesn't exist, thats a problem.

I checked J2SE 1.4 and 1.5, and in both, Book() is only constructor.

Please let me know whats going on, maybe I can help.

[mariejt]

I also have a Book class. Book 2 is a subclass of Book. I'm still baffled as to why I can't creat an object of Book or Book2 as they both exisit......

Thanks!

I've attached my Book code:

public class Book // Book has four attributes
{

	private String bookTitle = "";	
	private int itemNumber = 0;
	private int bookUnits = 0;
	private double bookPrice = 0.00;

	// Book constructor
	public Book (String bookTitle, int itemNumber, int bookUnits, double bookPrice)
	{
		this.bookTitle = bookTitle; // initializes bookTitle for Book		
		this.itemNumber = itemNumber; // initializes itemNumber for Book
		this.bookUnits = bookUnits; // initializes bookUnits for Book
		this.bookPrice = bookPrice; // initializes bookPrice for Book
	} // end constructor
	
	// method to set the book title
	public void setBookTitle (String bookTitle)
	{
		this.bookTitle = bookTitle;
	} // end method setBookTitle

	// method to retrieve the book title
	public String getBookTitle()
	{
		return bookTitle;
	} // end method getBookTitle

	// method to set the item number
	public void setItemNumber (int itemNumber)
	{
		this.itemNumber = itemNumber;
	} // end method setItemNumber

	// method to retrieve the item number
	public int getItemNumber()
	{
		return itemNumber;
	} // end method getItemNumber

	// method to set the book units
	public void setBookUnits (int bookUnits)
	{
		this.bookUnits = bookUnits;
	} // end method setBookUnits

	// method to retrieve the book units
	public int getBookUnits()
	{
		return bookUnits;
	} // end method getBookUnits

	// method to set the book price
	public void setBookPrice (double bookPrice)
	{
		this.bookPrice = bookPrice;
	} // end method setBookPrice

	// method to retrieve the book price
	public double getBookPrice()
	{
		return bookPrice;
	} // end method getBookPrice

	// method to calculate the inventory value
	public double inventoryValue()
	{
		return bookPrice * bookUnits;
	} // end method inventoryValue

} // end class Book

[cms271828]

Ok, this is easy...

If you dont have any constructors in your class, then you automatically get the default one for free...
Book()

You have a constructor..Book(a,b,c)
So therefore, you do not get the default no-args constructor, if you want it, you must put it in explicity as well.

Book2() { }

Book2(a,b,c) { // some code }

Hope that helps

[mariejt]

Awesome - Thank you so much!!!!!!!

[parthiban]

Hi mariejt,

I am trying to create a Book2 object and assign to Inventory_Program6a. When I try the following: Book2 newBookTitle = Book2();

Book2 newBookTitle = new Book2(); The problem is you didn't declare default constructor in both Book and Book2
.So Simply add Book() and Book2() constructors in their respective classes .

One more thing use "code=java" while posting the code so that it will provide syntax highlighting which makes easy to read it.

greetings
Parthiban

[cms271828]

Another point to note...
If you do not call super(...) in your constructor, then it is called automatically for you on the default no-args constructor of the super class.

So supposing in super class you only had...
Book(int a,int b,int c){ }

Then if you DONT call super in book2's constructors, it will try to invoke Book(), and it will not compile.

This is a common question that comes up in java exams, and worth knowing about.