从Java开始，从控制结构到数据结构，第3版，第833页>>）写过它（四重检查！），每次，它抛出8“找不到符号出现在同一行上的错误，我无法弄清楚自己在做什么错。 这是我的代码：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
/**
* The OrderCalculatorGUI class creates the GUI for the Brandi's Bagel House application
*/
public class OrderCalculatorGUI extends JFrame
{
private BagelPanel bagels;
private ToppingPanel toppings;
private CofeePanel coffee;
private GreetingPanel banner;
private JPanel buttonPanel;
private JButton calcButton;
private JButton exitButton;
private final double TAX_RATE = 0.06;
/**
* Constructor
*/
public OrderCalculatorGUI()
{
//Display a title.
setTitle("Order Calculator");
//Specify an action for the close button.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//create a orderLayout manager.
setLayout(new BorderLayout());
// Create the custom panels.
banner = new GreetingPanel();
bagels = new BagelPanel();
toppings = new ToppingPanel();
coffee = new CoffeePanel();
// Create the button panel.
buildButtonPanel();
//Add the components to the content pane.
add(banner, BorderLayout.NORTH);
add(bagels, BorderLayout.WEST);
add(toppings, BorderLayout.CENTER);
add(coffee, BorderLayout.EAST);
add(buttonPanel, BorderLayout.SOUTH);
//Pack the contents of the window and display it.
pack();
setVisible(true);
}
/**
* The buildButtonPanel method builds the button panel.
*/
private void buildButtonPanel()
{
//Create a panel for the buttons.
buttonPanel = new JPanel();
//Create the buttons.
calcButton = new JButton("Calculate");
exitButton = new JButton("Exit");
//Register the action listeners.
calcButton.addActionListener(new CalcButtonListener());
exitButton.addActionListener(new ExitButtonListener());
//Add the buttons to the button panel.
buttonPanel.add(calcButton);
buttonPanel.add(exitButton);
}
/**
* Private inner class that handles the event when
* the user clicks the Calculate button.
*/
private class CalcButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
// Variables to hold the subtotal, tax, and total
double subtotal, tax, total;
//Calculate the subtotal.
subtotal = bagels.getBagelCost() +
toppings.getToppingCost() +
coffee.getCoffeeCost();
//Calculate the sales tax.
tax = subtotal * TAX_RATE;
//Calculate the total.
total = subtotal * TAX_RATE;
//Calculate the total.
total = subtotal + tax;
//Display the charges.
JOptionPane.showMessageDialog(null,
String.format("Subtotal: $%,.2f\n" +
"Tax: $%,.2f\n" +
"Total: $%,.2f",
subtotal, tax, total));
}
}
/**
* Private inner class that handles the event when
* the user clicks the Exit button.
*/
private class ExitButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
System.exit(0);
}
}
/**
* main method
*/
public static void main(String[] args)
{
new OrderCalculatorGUI();
}
}
这是在运行“ javac OrderCalculatorGUI.java”后cmd提示符下的控制台输出
OrderCalculatorGUI.java:11: error: cannot find symbol
private BagelPanel bagels;
^
symbol: class BagelPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:12: error: cannot find symbol
private ToppingPanel toppings;
^
symbol: class ToppingPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:13: error: cannot find symbol
private CofeePanel coffee;
^
symbol: class CofeePanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:14: error: cannot find symbol
private GreetingPanel banner;
^
symbol: class GreetingPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:36: error: cannot find symbol
banner = new GreetingPanel();
^
symbol: class GreetingPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:37: error: cannot find symbol
bagels = new BagelPanel();
^
symbol: class BagelPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:38: error: cannot find symbol
toppings = new ToppingPanel();
^
symbol: class ToppingPanel
location: class OrderCalculatorGUI
OrderCalculatorGUI.java:39: error: cannot find symbol
coffee = new CoffeePanel();
^
symbol: class CoffeePanel
location: class OrderCalculatorGUI
8 errors
至此，我有些困惑。我不确定发生了什么问题，正在犯什么愚蠢的错误或其他奇怪的异常情况。感谢您的协助。
谢谢！
我正在从Java教科书中编写程序，作为编写类似程序的练习。我写的与我们的书中所写的完全一样（从Java开始，来自控件结构...
[建议您阅读课程材料并找到合适的代码，然后重试，或者如果找不到，请在此处附上本书代码的图片。