用java实现简易记事本

这是一个简单的Java Swing记事本示例：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.text.DefaultEditorKit;

public class SimpleNotepad extends JFrame implements ActionListener {
    private JTextArea textArea;
    private JLabel statusBar;
    private JFileChooser fileChooser;
    private String currentFile = "";
    private JMenuBar menuBar;
    private JMenu fileMenu, editMenu, formatMenu, viewMenu, helpMenu;
    private JMenuItem newFile, openFile, saveFile, saveAsFile, pageSetup, printFile, exitProgram;
    private JMenuItem undoEdit, cutEdit, copyEdit, pasteEdit, deleteEdit, findEdit, findNextEdit, replaceEdit, gotoEdit, selectAllEdit, timeDateEdit;
    private JMenuItem wordWrapFormat, fontFormat;
    private JMenuItem statusBarView;
    private JMenuItem aboutHelp;

    public SimpleNotepad() {
        super("Simple Notepad");

        // Create the text area and set the font
        textArea = new JTextArea();
        textArea.setFont(new Font("Monospaced", Font.PLAIN, 12));

        // Add the text area to a scroll pane
        JScrollPane scrollPane = new JScrollPane(textArea);
        scrollPane.setPreferredSize(new Dimension(800, 600));

        // Add the scroll pane to the frame
        add(scrollPane, BorderLayout.CENTER);

        // Create the status bar
        statusBar = new JLabel("Ready");
        statusBar.setBorder(BorderFactory.createEtchedBorder(Color.WHITE, Color.BLACK));
        add(statusBar, BorderLayout.SOUTH);

        // Create the file chooser
        fileChooser = new JFileChooser(".");
        fileChooser.setFileFilter(new FileNameExtensionFilter("Text Files (*.txt)", "txt"));

        // Create the menu bar
        menuBar = new JMenuBar();

        // Create the file menu
        fileMenu = new JMenu("File");
        fileMenu.setMnemonic('F');
        newFile = new JMenuItem("New");
        newFile.setAccelerator(KeyStroke.getKeyStroke("control N"));
        newFile.addActionListener(this);
        fileMenu.add(newFile);
        openFile = new JMenuItem("Open");
        openFile.setAccelerator(KeyStroke.getKeyStroke("control O"));
        openFile.addActionListener(this);
        fileMenu.add(openFile);
        saveFile = new JMenuItem("Save");
        saveFile.setAccelerator(KeyStroke.getKeyStroke("control S"));
        saveFile.addActionListener(this);
        fileMenu.add(saveFile);
        saveAsFile = new JMenuItem("Save As...");
        saveAsFile.addActionListener(this);
        fileMenu.add(saveAsFile);
        fileMenu.addSeparator();
        pageSetup = new JMenuItem("Page Setup...");
        pageSetup.addActionListener(this);
        fileMenu.add(pageSetup);
        printFile = new JMenuItem("Print...");
        printFile.setAccelerator(KeyStroke.getKeyStroke("control P"));
        printFile.addActionListener(this);
        fileMenu.add(printFile);
        fileMenu.addSeparator();
        exitProgram = new JMenuItem("Exit");
        exitProgram.setAccelerator(KeyStroke.getKeyStroke("alt F4"));
        exitProgram.addActionListener(this);
        fileMenu.add(exitProgram);
        menuBar.add(fileMenu);

        // Create the edit menu
        editMenu = new JMenu("Edit");
        editMenu.setMnemonic('E');
        undoEdit = new JMenuItem("Undo");
        undoEdit.setAccelerator(KeyStroke.getKeyStroke("control Z"));
        undoEdit.addActionListener(this);
        editMenu.add(undoEdit);
        editMenu.addSeparator();
        cutEdit = new JMenuItem(new DefaultEditorKit.CutAction());
        cutEdit.setText("Cut");
        cutEdit.setAccelerator(KeyStroke.getKeyStroke("control X"));
        editMenu.add(cutEdit);
        copyEdit = new JMenuItem(new DefaultEditorKit.CopyAction());
        copyEdit.setText("Copy");
        copyEdit.setAccelerator(KeyStroke.getKeyStroke("control C"));
        editMenu.add(copyEdit);
        pasteEdit = new JMenuItem(new DefaultEditorKit.PasteAction());
        pasteEdit.setText("Paste");
        pasteEdit.setAccelerator(KeyStroke.getKeyStroke("control V"));
        editMenu.add(pasteEdit);
        deleteEdit = new JMenuItem("Delete");
        deleteEdit.setAccelerator(KeyStroke.getKeyStroke("DELETE"));
        deleteEdit.addActionListener(this);
        editMenu.add(deleteEdit);
        editMenu.addSeparator();
        findEdit = new JMenuItem("Find...");
        findEdit.setAccelerator(KeyStroke.getKeyStroke("control F"));
        findEdit.addActionListener(this);
        editMenu.add(findEdit);
        findNextEdit = new JMenuItem("Find Next");
        findNextEdit.setAccelerator(KeyStroke.getKeyStroke("F3"));
        findNextEdit.addActionListener(this);
        editMenu.add(findNextEdit);
        replaceEdit = new JMenuItem("Replace...");
        replaceEdit.setAccelerator(KeyStroke.getKeyStroke("control H"));
        replaceEdit.addActionListener(this);
        editMenu.add(replaceEdit);
        gotoEdit = new JMenuItem("Go To...");
        gotoEdit.setAccelerator(KeyStroke.getKeyStroke("control G"));
        gotoEdit.addActionListener(this);
        editMenu.add(gotoEdit);
        editMenu.addSeparator();
        selectAllEdit = new JMenuItem("Select All");
        selectAllEdit.setAccelerator(KeyStroke.getKeyStroke("control A"));
        selectAllEdit.addActionListener(this);
        editMenu.add(selectAllEdit);
        timeDateEdit = new JMenuItem("Time/Date");
        timeDateEdit.setAccelerator(KeyStroke.getKeyStroke("F5"));
        timeDateEdit.addActionListener(this);
        editMenu.add(timeDateEdit);
        menuBar.add(editMenu);

        // Create the format menu
        formatMenu = new JMenu("Format");
        formatMenu.setMnemonic('O');
        wordWrapFormat = new JMenuItem("Word Wrap");
        wordWrapFormat.addActionListener(this);
        formatMenu.add(wordWrapFormat);
        fontFormat = new JMenuItem("Font...");
        fontFormat.addActionListener(this);
        formatMenu.add(fontFormat);
        menuBar.add(formatMenu);

        // Create the view menu
        viewMenu = new JMenu("View");
        viewMenu.setMnemonic('V');
        statusBarView = new JMenuItem("Status Bar");
        statusBarView.addActionListener(this);
        viewMenu.add(statusBarView);
        menuBar.add(viewMenu);

        // Create the help menu
        helpMenu = new JMenu("Help");
        helpMenu.setMnemonic('H');
        aboutHelp = new JMenuItem("About Simple Notepad");
        aboutHelp.addActionListener(this);
        helpMenu.add(aboutHelp);
        menuBar.add(helpMenu);

        // Add the menu bar to the frame
        setJMenuBar(menuBar);

        // Set the frame properties
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(800, 600);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == newFile) {
            newFile();
        } else if (e.getSource() == openFile) {
            openFile();
        } else if (e.getSource() == saveFile) {
            saveFile();
        } else if (e.getSource() == saveAsFile) {
            saveAsFile();
        } else if (e.getSource() == pageSetup) {
            pageSetup();
        } else if (e.getSource() == printFile) {
            printFile();
        } else if (e.getSource() == exitProgram) {
            exitProgram();
        } else if (e.getSource() == undoEdit) {
            undoEdit();
        } else if (e.getSource() == deleteEdit) {
            deleteEdit();
        } else if (e.getSource() == findEdit) {
            findEdit();
        } else if (e.getSource() == findNextEdit) {
            findNextEdit();
        } else if (e.getSource() == replaceEdit) {
            replaceEdit();
        } else if (e.getSource() == gotoEdit) {
            gotoEdit();
        } else if (e.getSource() == selectAllEdit) {
            selectAllEdit();
        } else if (e.getSource() == timeDateEdit) {
            timeDateEdit();
        } else if (e.getSource() == wordWrapFormat) {
            wordWrapFormat();
        } else if (e.getSource() == fontFormat) {
            fontFormat();
        } else if (e.getSource() == statusBarView) {
            statusBarView();
        } else if (e.getSource() == aboutHelp) {
            aboutHelp();
        }
    }

    private void newFile() {
        currentFile = "";
        textArea.setText("");
        setTitle("Simple Notepad");
    }

    private void openFile() {
        int result = fileChooser.showOpenDialog(this);
        if (result == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                BufferedReader reader = new BufferedReader(new FileReader(file));
                String line;
                StringBuilder text = new StringBuilder();
                while ((line = reader.readLine()) != null) {
                    text.append(line).append("\n");
                }
                reader.close();
                textArea.setText(text.toString());
                currentFile = file.getAbsolutePath();
                setTitle("Simple Notepad - " + file.getName());
            } catch (IOException e) {
                statusBar.setText("Error: " + e.getMessage());
            }
        }
    }

    private void saveFile() {
        if (currentFile.isEmpty()) {
            saveAsFile();
        } else {
            try {
                FileWriter writer = new FileWriter(currentFile);
                writer.write(textArea.getText());
                writer.close();
                setTitle("Simple Notepad - " + new File(currentFile).getName());
            } catch (IOException e) {
                statusBar.setText("Error: " + e.getMessage());
            }
        }
    }

    private void saveAsFile() {
        int result = fileChooser.showSaveDialog(this);
        if (result == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                FileWriter writer = new FileWriter(file);
                writer.write(textArea.getText());
                writer.close();
                currentFile = file.getAbsolutePath();
                setTitle("Simple Notepad - " + file.getName());
            } catch (IOException e) {
                statusBar.setText("Error: " + e.getMessage());
            }
        }
    }

    private void pageSetup() {
        // TODO: Implement page setup functionality
    }

    private void printFile() {
        // TODO: Implement printing functionality
    }

    private void exitProgram() {
        System.exit(0);
    }

    private void undoEdit() {
        // TODO: Implement undo functionality
    }

    private void deleteEdit() {
        textArea.replaceSelection("");
    }

    private void findEdit() {
        // TODO: Implement find functionality
    }

    private void findNextEdit() {
        // TODO: Implement find next functionality
    }

    private void replaceEdit() {
        // TODO: Implement replace functionality
    }

    private void gotoEdit() {
        // TODO: Implement goto functionality
    }

    private void selectAllEdit() {
        textArea.selectAll();
    }

    private void timeDateEdit() {
        textArea.insert(new java.util.Date().toString(), textArea.getCaretPosition());
    }

    private void wordWrapFormat() {
        textArea.setLineWrap(!textArea.getLineWrap());
        wordWrapFormat.setSelected(textArea.getLineWrap());
    }

    private void fontFormat() {
        // TODO: Implement font selection functionality
    }

    private void statusBarView() {
        statusBar.setVisible(!statusBar.isVisible());
        statusBarView.setSelected(statusBar.isVisible());
    }

    private void aboutHelp() {
        JOptionPane.showMessageDialog(this, "Simple Notepad\n\nCreated by Your Name Here", "About Simple Notepad", JOptionPane.INFORMATION_MESSAGE);
    }

    public static void main(String[] args) {
        new SimpleNotepad();
    }
}

这个记事本利用了Java Swing库的许多组件和功能，包括文本区域、滚动窗格、菜单、菜单项、对话框等。它可以打开、保存、打印、撤消、剪切、复制、粘贴和删除文本，还可以查找、替换、跳转、全选、插入时间/日期，以及调整字体和文本包装等。