[Eku]

here it is. I didnt change anything in your Calculation Class. I only modify the main class.

Code:

import java.text.DecimalFormat;
import javax.swing.*;
import java.awt.Color;
import java.awt.Font;
import java.awt.event.*;


public class Main extends JFrame implements ActionListener
{   private Calculation myOrder = new Calculation();
	 // All the GUI objects
    JPanel mainPanel = new JPanel();
    JLabel storeLabel = new JLabel("       OrderBook INC.         ");
    JTextField bookNameTextField = new JTextField(20);
    JTextField quantityTextField = new JTextField(20);
    JTextField priceTextField = new JTextField(20);
    JButton calculateButton = new JButton(" Calculate   ");
    JTextArea outputTextArea = new JTextArea("Books Ordered", 10, 25);
    JScrollPane outputScrollPane = new JScrollPane(outputTextArea);
	
	int quantityInteger;
	double priceDouble;
	String nameString;
	
    //object of the font
    Font storeFont = new Font("Arial",Font.BOLD,14);

	public static void main(String[] args)
	{
		Main myBooks = new Main();
		myBooks.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

	}
	
	public Main()
	{
		designFrame();
		
	}
	
	
	public void designFrame()
	{
        //set the font and the color
        storeLabel.setFont(storeFont);
        storeLabel.setForeground(Color.GRAY);
        
                //add the listeners
//        priceTextField.addActionListener(this);
        calculateButton.addActionListener(this);
    
        //add the components to the mainPanel
        mainPanel.add(storeLabel);
        mainPanel.add(new JLabel("       Book Name            "));
        mainPanel.add(bookNameTextField);
        mainPanel.add(new JLabel("    Quantity Ordered   "));
        mainPanel.add(quantityTextField);
        mainPanel.add(new JLabel("    Price       "));
        mainPanel.add(priceTextField);
        mainPanel.add(calculateButton);
        mainPanel.add(outputScrollPane);
        

                
        //add the panel to the frame
        add(mainPanel);
        setSize(300,400);
        setVisible(true);
	}
	
	
	public void actionPerformed(ActionEvent evt)
	{ String cmd = evt.getActionCommand();
          if (cmd.equalsIgnoreCase(" Calculate   ")){
              nameString = bookNameTextField.getText();
	      quantityInteger = Integer.parseInt(quantityTextField.getText());
	      priceDouble = Double.parseDouble(priceTextField.getText());
              myOrder.Calculation(quantityInteger, priceDouble);
              displayOutput();
          }

	clear();
	}
	public void displayOutput() 
    {
        
		//object to format to currency
        DecimalFormat formatDecimalFormat = new DecimalFormat("$0.00");
        DecimalFormat formatNumberFormat = new DecimalFormat("0");
        //variables to store the retrieved values from the calculation class
        double  priceDouble, subTotalDouble, shippingDouble, taxDouble, totalDouble, 
        grandTotalDouble;
        int totalNumberOfOrdersInteger;
          
        priceDouble = myOrder.getPrice(); System.out.println(priceDouble);
        subTotalDouble = myOrder.getSubTotal();
        shippingDouble = myOrder.getShipping();
        taxDouble = myOrder.getTax();
        totalDouble = myOrder.getTotal();
        grandTotalDouble = myOrder.getGrandTotal();
        totalNumberOfOrdersInteger = myOrder.getNumberOfOrders();
        
        //display output
        outputTextArea.append('\n' + "Name of the Book: " + nameString + '\n' + 
        		"Quantity Ordered: " + formatNumberFormat.format(quantityInteger)
        		+ '\n' + "Price: 	" + formatDecimalFormat.format(priceDouble)+ '\n'
        		+ '\n' + "Subtotal: 	" + formatDecimalFormat.format(subTotalDouble)
        		+ '\n' + "Shipping: 	" + formatDecimalFormat.format(shippingDouble)
        		+ '\n' + "Tax: 	" + formatDecimalFormat.format(taxDouble) + '\n'+ 
        		"Total:	" +	formatDecimalFormat.format(totalDouble) + '\n' +'\n' + 
        		"Total Quantity To-Date: " + totalNumberOfOrdersInteger + '\n' + 
        		" Grand Total To-Date: " + formatDecimalFormat.format(grandTotalDouble)
        		+ '\n');      
        return;
    }
   
    public void  clear()
    {
    	//clear existing text from text fields and request cursor to top
    	bookNameTextField.setText("");
        quantityTextField.setText("");
        priceTextField.setText("");
        bookNameTextField.requestFocus();        
    }    
}

I hope that helps. -Eku