Java 我正在尝试实施和'；撤消'；JButton在一个简单的银行系统上，它将撤消最后执行的操作

我已经运行了其余的代码，但是我不确定在ActionListener中对Undo按钮做什么。我只有行动听众才能做到这一点

    private class UndoButtonHandler implements ActionListener{

    public void actionPerformed(ActionEvent e) {

    }

我将在下面发布GUI类的其余部分以供参考，因为这不是一个任务（它是，只是不在GUI中），我感谢任何人能给我的建议

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


    public class BankGUI extends JFrame {
private JLabel checking;
private JLabel saving;
private JButton depChecking;
private JButton depSaving;
private JButton witChecking;
private JButton withSaving;
private JButton transferToSaving;
private JButton transferToChecking;
private JButton undo;
private JTextField checkingAmt;
private JTextField savingAmt;
private JTextField depositChk;
private JTextField depositSav;
private JTextField withChk;
private JTextField withSav;
private JTextField transChk;
private JTextField transSav;

public BankGUI() {
    super( "Bank Application" );
    setLayout(new FlowLayout() );

    checkingAmt = new JTextField(10);
    checkingAmt.setEditable(false);
    checkingAmt.setText("500.00");
    add( checkingAmt );

    savingAmt = new JTextField(10);
    savingAmt.setEditable(false);
    savingAmt.setText("0.00");
    add(savingAmt);

    checking = new JLabel( "                  Checking        ");
    add(checking);

    saving = new JLabel( "      Saving              " );
    add(saving);

    depChecking = new JButton( "  Deposit  " );
    add(depChecking);
    depChecking.addActionListener(new DepChkButtonHandler());

    depSaving = new JButton( "  Deposit  " );
    add(depSaving);
    depSaving.addActionListener(new DepSavButtonHandler());

    depositChk = new JTextField(10);
    depositChk.setEditable(true);
    add(depositChk);

    depositSav = new JTextField(10);
    depositSav.setEditable(true);
    add(depositSav);

    witChecking = new JButton( "  Withdraw  " );
    add(witChecking);
    witChecking.addActionListener(new WitChkButtonHandler());

    withSaving = new JButton( "  Withdraw  " );
    add(withSaving);
    withSaving.addActionListener(new WithSavButtonHandler());

    withChk = new JTextField(10);
    withChk.setEditable(true);
    add(withChk);

    withSav = new JTextField(10);
    withSav.setEditable(true);
    add(withSav);

    transferToSaving = new JButton( "  Transfer  " );
    add(transferToSaving);
    transferToSaving.addActionListener(new TranstoSavButtonHandler());

    transferToChecking = new JButton( "  Transfer  " );
    add(transferToChecking);
    transferToChecking.addActionListener(new TranstoChkButtonHandler());

    transSav = new JTextField(10);
    transSav.setEditable(true);
    add(transSav);

    transChk = new JTextField(10);
    transChk.setEditable(true);
    add(transChk);

    undo = new JButton( "  Undo  " );
    add(undo);
}

private class DepChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent arg0) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double depAmt = Double.parseDouble(depositChk.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt = deciFormat.format(depAmt + chkAmt);

        checkingAmt.setText(newAmt);

    }

}

private class DepSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double depAmt = Double.parseDouble(depositSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        String newAmt = deciFormat.format(depAmt + savAmt);

        savingAmt.setText(newAmt);

    }

}

private class WitChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent arg0) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double witAmt = Double.parseDouble(withChk.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt = deciFormat.format(chkAmt - witAmt);

        checkingAmt.setText(newAmt);

    }

}

private class WithSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double witAmt = Double.parseDouble(withSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        String newAmt = deciFormat.format(savAmt - witAmt);

        savingAmt.setText(newAmt);

    }

}

private class TranstoSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double transAmt = Double.parseDouble(transSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt1 = deciFormat.format(savAmt + transAmt);
        String newAmt2 = deciFormat.format(chkAmt - transAmt);
        savingAmt.setText(newAmt1);
        checkingAmt.setText(newAmt2);

    }

}

private class TranstoChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double transAmt = Double.parseDouble(transChk.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt1 = deciFormat.format(savAmt - transAmt);
        String newAmt2 = deciFormat.format(chkAmt + transAmt);
        savingAmt.setText(newAmt1);
        checkingAmt.setText(newAmt2);

    }

}

private class UndoButtonHandler implements ActionListener{

    public void actionPerformed(ActionEvent e) {

    }
}

---

}您需要决定撤销的深度。用户可以撤消最后10个操作，还是仅撤消最近的操作？此决定将确定您是将最后一个操作存储为简单字段，还是存储为某种类型的

事务列表

（某种类型的

队列

也可以）

您还应该将事务规范化为某种模型，该模型可以反映应用程序支持的每种事务的详细信息。换句话说，您需要一个

交易

对象，其中包含

金额

、

源账户

、

目的账户

等字段，或者以您想要的方式执行。关键是，该事务对象需要能够表示用户可能希望在程序中执行（或撤消）的所有操作

此交易对象将用于正常记账（从帐户中添加或删除资金），但在调整余额后，您将交易保存到

lastTransaction

字段或

交易

列表中

---

创建一个名为

undo

的方法，并将其放入undo处理程序中。当用户单击“撤消”按钮时，您的

undo

方法只查看最近的事务并将其撤消。例如，如果交易是支票存款100美元，当您撤消它时，您将从支票中减去100美元，而不是向支票中添加100美元。如果您正在处理事务列表，请确保在撤消事务后将其删除。

现在只需执行最后一个操作，这是一个好主意！我整天忙于不同的项目，精神上受到了严重的阻碍，但我想你给了我一个新的想法。我很感激。