java - ClassCastException 异常处理和类创建需要帮助

Question

在同事的帮助下，我一直在努力修改我的代码，并取得了一些进展。我面临两个问题，希望得到帮助。首先是在我的 MyListener 类中。根据之前的教程和示例，我查看了使用的“JButton source = (JButton) e.getSource();”检查正在使用哪个操作。当我只使用按钮时这很好，但现在我有了单选按钮，它会抛出castClassException。不确定这个问题的解决方法。我面临的下一个问题是 InsufficientFunds 类，我在这些部分放置了大块引号以获得更好的可视化效果。该类设置为当余额低于请求提取或转账的金额时抛出异常。我为这些事件设置了手动触发器，因为我无法正确设置类来处理这种情况。我如何正确设置此类来处理异常，以及如何将它们实现到 Account 类下的正确事件中(这是应该使用它的地方)？最后，如果有人对我当前的代码有进一步的建议，我将不胜感激，因为我正在尝试完成该项目。

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.*;
import javax.swing.JFrame;

class Account {

private double balance;

public Account(double initialBalance) {
    balance = initialBalance;
}

public double getBalance() {
    return balance;
}

public void deposit(double amount) {
    balance += amount;
}

public void withdraw(double amount) {
    balance -= amount;

}
} // End class Account

class InsufficientFunds extends Exception {

/* 
 *
 *
 * Needs to create InsufficientFUnds() and be implemented in Account class
 *
 *
 */
} // End class InsufficientFunds

public class ATM extends JFrame {

private final JButton withdrawButton;
private final JButton depositButton;
private final JButton transferButton;
private final JButton balanceButton;
private final JRadioButton checkingRadio;
private final JRadioButton savingsRadio;
private final JTextField valueText;
private static final int FRAME_WIDTH = 325;
private static final int FRAME_HEIGHT = 200;

static Account checkingAccount;
static Account savingsAccount;

public ATM() {
    // Sets Frame and Layout
    setSize(FRAME_WIDTH, FRAME_HEIGHT);
    setTitle("ATM Machine");
    setResizable(false);
    setLocationRelativeTo(null);
    setLayout(new GridBagLayout());
    GridBagConstraints constraints = new GridBagConstraints();
    constraints.fill = GridBagConstraints.HORIZONTAL;

    // Create withdrawButton Button and places is on display
    withdrawButton = new JButton("Withdraw");
    constraints.insets = new Insets(5, 50, 2, 5);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.gridx = 0;
    constraints.gridy = 0;
    add(withdrawButton, constraints);

    // Create depositButton Button and places is on display
    depositButton = new JButton("Deposit");
    constraints.insets = new Insets(5, 5, 2, 50);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.gridx = 1;
    add(depositButton, constraints);

    // Create transferButton Button and places is on display
    transferButton = new JButton("Transfer To");
    constraints.insets = new Insets(1, 50, 2, 5);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.gridx = 0;
    constraints.gridy = 2;
    add(transferButton, constraints);

    // Create balanceButton Button and places is on display
    balanceButton = new JButton("Balance");
    constraints.insets = new Insets(1, 5, 2, 50);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.gridx = 1;
    add(balanceButton, constraints);

    // Create checkingRadio RadioButton and places is on display
    checkingRadio = new JRadioButton("Checking");
    constraints.insets = new Insets(1, 50, 5, 5);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.gridx = 0;
    constraints.gridy = 3;
    add(checkingRadio, constraints);

    // Create savingsRadio RadioButton and places is on display
    savingsRadio = new JRadioButton("Savings");
    constraints.insets = new Insets(1, 5, 5, 50);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.anchor = GridBagConstraints.PAGE_END;
    constraints.gridx = 1;
    add(savingsRadio, constraints);

    // Create valueText TextField and places is on display
    valueText = new JTextField(10);
    constraints.fill = GridBagConstraints.HORIZONTAL;
    constraints.insets = new Insets(1, 35, 30, 35);
    constraints.gridx = 0;
    constraints.gridwidth = 2;
    constraints.gridy = 4;
    add(valueText, constraints);

    //Group RadioButtons so that only one selection allowed
    ButtonGroup radioButtons = new ButtonGroup();
    radioButtons.add(checkingRadio);
    radioButtons.add(savingsRadio);

    // Group Buttons so that only one selection allowed
    ButtonGroup buttons = new ButtonGroup();
    buttons.add(withdrawButton);
    buttons.add(depositButton);
    buttons.add(transferButton);
    buttons.add(balanceButton);

    // Sets the frame open and close
    JFrame frame = new JFrame("ATM Machine");
    frame.pack();
    frame.getContentPane();
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Adds ActionListeners to each of the Buttons
    withdrawButton.addActionListener(new MyListener());
    depositButton.addActionListener(new MyListener());
    transferButton.addActionListener(new MyListener());
    balanceButton.addActionListener(new MyListener());
    checkingRadio.addActionListener(new MyListener());
    savingsRadio.addActionListener(new MyListener());
    valueText.addActionListener(new MyListener());
}

// Handles Events for the JButtons
class MyListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {

        JButton source = (JButton) e.getSource();

        if ("Withdraw".equalsIgnoreCase(source.getText())) {
            if (checkingRadio.isSelected()) {
                try {
                    String amountString = valueText.getText();
                    double withdrawAmount = Double.parseDouble(amountString);
                    if (withdrawAmount % 20 == 0) {
                        if (withdrawAmount <= checkingAccount.getBalance()) {
                                checkingAccount.withdraw(Double.parseDouble(valueText.getText()));
                            JOptionPane.showMessageDialog(null, "Withdraw Complete");
                        } else {
                            JOptionPane.showMessageDialog(null, "Insufficient Funds");
                        }
                    } else {
                        JOptionPane.showMessageDialog(null, "Please Use Increments of $20");
                    }
                } catch (NumberFormatException nfe) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End withdraw/checking

            if (savingsRadio.isSelected()) {
                try {
                    String amountString = valueText.getText();
                    double withdrawAmount = Double.parseDouble(amountString);
                    if (withdrawAmount % 20 == 0) {
                        if (withdrawAmount <= savingsAccount.getBalance()) {
                            savingsAccount.withdraw(Double.parseDouble(valueText.getText()));
                            JOptionPane.showMessageDialog(null, "Withdraw Complete");
                        } else {
                            JOptionPane.showMessageDialog(null, "Insufficient Funds");
                        }
                    } else {
                        JOptionPane.showMessageDialog(null, "Please Use Increments of $20");
                    }
                } catch (NumberFormatException nfe) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End withdraw/savings


            valueText.setText("");
        } // End Withdraw Events

        if ("Deposit".equalsIgnoreCase(source.getText())) {
            if (checkingRadio.isSelected()) {
                try {
                    checkingAccount.deposit(Double.parseDouble(valueText.getText()));
                    JOptionPane.showMessageDialog(null, "Deposit Complete ");
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End deposit/checking
            if (savingsRadio.isSelected()) {
                try {
                    savingsAccount.deposit(Double.parseDouble(valueText.getText()));
                    JOptionPane.showMessageDialog(null, "Deposit Complete");
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End deposit/savings
            valueText.setText("");
        } // End Deposit Events

        if ("Transfer To".equalsIgnoreCase(source.getText())) {
            if (checkingRadio.isSelected()) {
                try {
                    String amountString = valueText.getText();
                    double transferAmount = Double.parseDouble(amountString);
                    if (transferAmount <= savingsAccount.getBalance()) {
                        savingsAccount.withdraw(transferAmount);
                        checkingAccount.deposit(transferAmount);
                        JOptionPane.showMessageDialog(null, "Transfer Complete ");
                    } else {
                        JOptionPane.showMessageDialog(null, "Insufficient Funds");
                    }
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End transfer/checking
            if (savingsRadio.isSelected()) {
                try {
                    String amountString = valueText.getText();
                    double transferAmount = Double.parseDouble(amountString);
                    if (transferAmount <= checkingAccount.getBalance()) {

                        checkingAccount.withdraw(transferAmount);
                        savingsAccount.deposit(transferAmount);
                        JOptionPane.showMessageDialog(null, "Transfer Complete ");
                    } else {
                        JOptionPane.showMessageDialog(null, "Insufficient Funds");
                    }
                } catch (NumberFormatException ex) {
                    JOptionPane.showMessageDialog(null, "Please Enter a Numerical Value");
                }
            } // End transfer/savings


            valueText.setText("");
        } // End Transfer Events

        if ("Balance".equalsIgnoreCase(source.getText())) {
            double currentBalance;
            DecimalFormat df = new DecimalFormat("###,###,###,###,##0.00");

            if (checkingRadio.isSelected()) {
                currentBalance = checkingAccount.getBalance();
                JOptionPane.showMessageDialog(null, "Current Balance: $" + df.format(currentBalance));
            } else if (savingsRadio.isSelected()) {
                currentBalance = savingsAccount.getBalance();
                JOptionPane.showMessageDialog(null, "Current Balance: $" + df.format(currentBalance));
            } else {
                JOptionPane.showMessageDialog(null, "Please Select an Account");
            }
        } // End Balance Events
    } // End ActionPerformed
}  // End class myListener

public static void main(String[] args) {
    ATM atm = new ATM();
    // Checking and Savings Objects
    checkingAccount = new Account(0);
    savingsAccount = new Account(0);
} // End Main
} // End class ATM

Answer 1

I need an event handler that ensure the data typed in the TextField is numeric

使用应用于 JTextField 的 Document 的 DocumentFilter 来限制可以在其中输入的内容。

看看Implementing a Document Filter和 DocumentFilter Examples了解更多详情。

您还可以使用 JSpinner 或 JFormattedTextField 来获得或多或少相同的结果，请参阅 How to Use Spinners和 How to Use Formatted Text Fields了解更多详情

also only checking or savings RadioButtons are selected at one time

使用 ButtonGroup 将该组中所选项目的数量限制为单个项目

参见How to Use the ButtonGroup Component了解更多详情