Java 编写一个记事本软件，实现纯文本文件的新建、打开、保存、另存、复制、粘贴、查找、替换、关于等等功能；关闭软件是弹出对话框提示是否把修改保存的代码

以下是一个简单的记事本软件实现的示例代码，其中包括了新建、打开、保存、另存、复制、粘贴、查找、替换等功能，以及关闭软件时弹出对话框提示是否保存修改。

import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.text.DefaultEditorKit;
import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class Notepad extends JFrame {
    private JTextArea textArea;
    private JFileChooser fileChooser;

    private boolean isModified = false;
    private String filePath = "";

    public Notepad() {
        setTitle("记事本");
        setSize(800, 600);
        setLocationRelativeTo(null);

        textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane(textArea);
        add(scrollPane);

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);

        JMenu fileMenu = new JMenu("文件(F)");
        fileMenu.setMnemonic(KeyEvent.VK_F);
        menuBar.add(fileMenu);

        JMenuItem newMenuItem = new JMenuItem("新建(N)");
        newMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, InputEvent.CTRL_DOWN_MASK));
        newMenuItem.addActionListener(new NewActionListener());
        fileMenu.add(newMenuItem);

        JMenuItem openMenuItem = new JMenuItem("打开(O)");
        openMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, InputEvent.CTRL_DOWN_MASK));
        openMenuItem.addActionListener(new OpenActionListener());
        fileMenu.add(openMenuItem);

        JMenuItem saveMenuItem = new JMenuItem("保存(S)");
        saveMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, InputEvent.CTRL_DOWN_MASK));
        saveMenuItem.addActionListener(new SaveActionListener());
        fileMenu.add(saveMenuItem);

        JMenuItem saveAsMenuItem = new JMenuItem("另存为(A)");
        saveAsMenuItem.addActionListener(new SaveAsActionListener());
        fileMenu.add(saveAsMenuItem);

        fileMenu.addSeparator();

        JMenuItem exitMenuItem = new JMenuItem("退出(X)");
        exitMenuItem.addActionListener(new ExitActionListener());
        fileMenu.add(exitMenuItem);

        JMenu editMenu = new JMenu("编辑(E)");
        editMenu.setMnemonic(KeyEvent.VK_E);
        menuBar.add(editMenu);

        JMenuItem cutMenuItem = new JMenuItem(new DefaultEditorKit.CutAction());
        cutMenuItem.setText("剪切(T)");
        cutMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, InputEvent.CTRL_DOWN_MASK));
        editMenu.add(cutMenuItem);

        JMenuItem copyMenuItem = new JMenuItem(new DefaultEditorKit.CopyAction());
        copyMenuItem.setText("复制(C)");
        copyMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, InputEvent.CTRL_DOWN_MASK));
        editMenu.add(copyMenuItem);

        JMenuItem pasteMenuItem = new JMenuItem(new DefaultEditorKit.PasteAction());
        pasteMenuItem.setText("粘贴(P)");
        pasteMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, InputEvent.CTRL_DOWN_MASK));
        editMenu.add(pasteMenuItem);

        editMenu.addSeparator();

        JMenuItem findMenuItem = new JMenuItem("查找(F)");
        findMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F, InputEvent.CTRL_DOWN_MASK));
        findMenuItem.addActionListener(new FindActionListener());
        editMenu.add(findMenuItem);

        JMenuItem replaceMenuItem = new JMenuItem("替换(R)");
        replaceMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_H, InputEvent.CTRL_DOWN_MASK));
        replaceMenuItem.addActionListener(new ReplaceActionListener());
        editMenu.add(replaceMenuItem);

        JMenu helpMenu = new JMenu("帮助(H)");
        helpMenu.setMnemonic(KeyEvent.VK_H);
        menuBar.add(helpMenu);

        JMenuItem aboutMenuItem = new JMenuItem("关于记事本(A)");
        aboutMenuItem.addActionListener(new AboutActionListener());
        helpMenu.add(aboutMenuItem);

        fileChooser = new JFileChooser();
        FileNameExtensionFilter txtFilter = new FileNameExtensionFilter("文本文件(*.txt)", "txt");
        fileChooser.setFileFilter(txtFilter);

        addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                if (isModified) {
                    int choice = JOptionPane.showConfirmDialog(Notepad.this, "是否保存修改？", "记事本",
                            JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.WARNING_MESSAGE);
                    if (choice == JOptionPane.YES_OPTION) {
                        saveFile();
                    } else if (choice == JOptionPane.CANCEL_OPTION) {
                        return;
                    }
                }
                dispose();
            }
        });
    }

    private class NewActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (isModified) {
                int choice = JOptionPane.showConfirmDialog(Notepad.this, "是否保存修改？", "记事本",
                        JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.WARNING_MESSAGE);
                if (choice == JOptionPane.YES_OPTION) {
                    saveFile();
                } else if (choice == JOptionPane.CANCEL_OPTION) {
                    return;
                }
            }
            textArea.setText("");
            isModified = false;
            filePath = "";
        }
    }

    private class OpenActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (isModified) {
                int choice = JOptionPane.showConfirmDialog(Notepad.this, "是否保存修改？", "记事本",
                        JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.WARNING_MESSAGE);
                if (choice == JOptionPane.YES_OPTION) {
                    saveFile();
                } else if (choice == JOptionPane.CANCEL_OPTION) {
                    return;
                }
            }
            int result = fileChooser.showOpenDialog(Notepad.this);
            if (result == JFileChooser.APPROVE_OPTION) {
                File file = fileChooser.getSelectedFile();
                try {
                    BufferedReader reader = new BufferedReader(new FileReader(file));
                    StringBuilder sb = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null) {
                        sb.append(line).append("\n");
                    }
                    reader.close();
                    textArea.setText(sb.toString());
                    isModified = false;
                    filePath = file.getAbsolutePath();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
    }

    private class SaveActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            saveFile();
        }
    }

    private class SaveAsActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            int result = fileChooser.showSaveDialog(Notepad.this);
            if (result == JFileChooser.APPROVE_OPTION) {
                File file = fileChooser.getSelectedFile();
                try {
                    BufferedWriter writer = new BufferedWriter(new FileWriter(file));
                    writer.write(textArea.getText());
                    writer.flush();
                    writer.close();
                    isModified = false;
                    filePath = file.getAbsolutePath();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
    }

    private class ExitActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (isModified) {
                int choice = JOptionPane.showConfirmDialog(Notepad.this, "是否保存修改？", "记事本",
                        JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.WARNING_MESSAGE);
                if (choice == JOptionPane.YES_OPTION) {
                    saveFile();
                } else if (choice == JOptionPane.CANCEL_OPTION) {
                    return;
                }
            }
            dispose();
        }
    }

    private class FindActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            String str = JOptionPane.showInputDialog(Notepad.this, "查找内容：", "查找", JOptionPane.PLAIN_MESSAGE);
            if (str != null) {
                String text = textArea.getText();
                int index = text.indexOf(str);
                if (index != -1) {
                    textArea.setCaretPosition(index);
                    textArea.select(index, index + str.length());
                } else {
                    JOptionPane.showMessageDialog(Notepad.this, "没有找到 \"" + str + "\"", "查找", JOptionPane.INFORMATION_MESSAGE);
                }
            }
        }
    }

    private class ReplaceActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            String findStr = JOptionPane.showInputDialog(Notepad.this, "查找内容：", "替换", JOptionPane.PLAIN_MESSAGE);
            if (findStr != null) {
                String replaceStr = JOptionPane.showInputDialog(Notepad.this, "替换为：", "替换", JOptionPane.PLAIN_MESSAGE);
                if (replaceStr != null) {
                    String text = textArea.getText();
                    int index = text.indexOf(findStr);
                    if (index != -1) {
                        textArea.replaceRange(replaceStr, index, index + findStr.length());
                        isModified = true;
                    } else {
                        JOptionPane.showMessageDialog(Notepad.this, "没有找到 \"" + findStr + "\"", "替换", JOptionPane.INFORMATION_MESSAGE);
                    }
                }
            }
        }
    }

    private class AboutActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            JOptionPane.showMessageDialog(Notepad.this, "Java记事本\n\n作者：xxx\n版本：1.0", "关于记事本", JOptionPane.INFORMATION_MESSAGE);
        }
    }

    private void saveFile() {
        if (filePath.isEmpty()) {
            int result = fileChooser.showSaveDialog(Notepad.this);
            if (result == JFileChooser.APPROVE_OPTION) {
                File file = fileChooser.getSelectedFile();
                try {
                    BufferedWriter writer = new BufferedWriter(new FileWriter(file));
                    writer.write(textArea.getText());
                    writer.flush();
                    writer.close();
                    isModified = false;
                    filePath = file.getAbsolutePath();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        } else {
            File file = new File(filePath);
            try {
                BufferedWriter writer = new BufferedWriter(new FileWriter(file));
                writer.write(textArea.getText());
                writer.flush();
                writer.close();
                isModified = false;
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        Notepad notepad = new Notepad();
        notepad.setVisible(true);
    }
}

在上述代码中，我们使用了 Swing 中的 JTextArea、JScrollPane、JMenuBar、JMenu、JMenuItem、JFileChooser 等组件实现了一个简单的记事本软件。在关闭软件时，我们使用了 JOptionPane.showConfirmDialog() 方法弹出一个对话框提示用户是否保存修改。在保存文件时，我们先判断文件路径是否为空，如果为空则弹出保存文件对话框，如果不为空则直接保存文件。在查找和替换功能中，我们使用了 JTextArea 的 indexOf() 和 replaceRange() 方法实现了查找和替换文本的功能。