java记事本代码

以下是 Java 编写的简单记事本代码示例：

import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class Notepad extends Frame implements ActionListener {
    MenuBar mb;
    TextArea ta;
    Menu file;
    MenuItem open, save, exit;
    FileDialog fd;
    String filename;

    public Notepad() {
        super("Untitled - Notepad");

        mb = new MenuBar();
        file = new Menu("File");
        open = new MenuItem("Open");
        save = new MenuItem("Save");
        exit = new MenuItem("Exit");
        open.addActionListener(this);
        save.addActionListener(this);
        exit.addActionListener(this);
        file.add(open);
        file.add(save);
        file.addSeparator();
        file.add(exit);
        mb.add(file);

        setMenuBar(mb);

        ta = new TextArea();
        add(ta);

        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        });

        setSize(600, 400);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent ae) {
        if (ae.getSource() == open) {
            fd = new FileDialog(this, "Open", FileDialog.LOAD);
            fd.setVisible(true);
            if (fd.getFile() != null) {
                filename = fd.getDirectory() + fd.getFile();
                setTitle(filename + " - Notepad");
                readFile();
            }
        } else if (ae.getSource() == save) {
            if (filename == null) {
                fd = new FileDialog(this, "Save", FileDialog.SAVE);
                fd.setVisible(true);
                if (fd.getFile() != null) {
                    filename = fd.getDirectory() + fd.getFile();
                    setTitle(filename + " - Notepad");
                    writeFile();
                }
            } else {
                writeFile();
            }
        } else {
            System.exit(0);
        }
    }

    private void readFile() {
        try {
            BufferedReader br = new BufferedReader(new FileReader(filename));
            String line;
            ta.setText("");
            while ((line = br.readLine()) != null) {
                ta.append(line + "\n");
            }
            br.close();
        } catch (IOException e) {
            System.out.println("Error: " + e);
        }
    }

    private void writeFile() {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(filename));
            bw.write(ta.getText());
            bw.close();
        } catch (IOException e) {
            System.out.println("Error: " + e);
        }
    }

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

该代码创建了一个简单的记事本程序，可以打开和保存文本文件。它使用了 AWT 和事件处理程序来实现用户界面和交互。