Java gui生成一个简易记事本

好的，以下是一个简易的记事本GUI的Java代码示例：

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

public class SimpleNotepad extends JFrame implements ActionListener {
    private JTextArea textArea = new JTextArea();
    private JMenuBar menuBar = new JMenuBar();
    private JMenu fileMenu = new JMenu("File");
    private JMenuItem newMenuItem = new JMenuItem("New");
    private JMenuItem openMenuItem = new JMenuItem("Open");
    private JMenuItem saveMenuItem = new JMenuItem("Save");
    private JMenuItem exitMenuItem = new JMenuItem("Exit");

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

        // Set the size of the window
        setSize(640, 480);

        // Set the location of the window
        setLocationRelativeTo(null);

        // Add the text area to the content pane
        getContentPane().add(textArea);

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

        // Add the file menu to the menu bar
        menuBar.add(fileMenu);

        // Add the menu items to the file menu
        fileMenu.add(newMenuItem);
        fileMenu.add(openMenuItem);
        fileMenu.add(saveMenuItem);
        fileMenu.addSeparator();
        fileMenu.add(exitMenuItem);

        // Add the action listeners to the menu items
        newMenuItem.addActionListener(this);
        openMenuItem.addActionListener(this);
        saveMenuItem.addActionListener(this);
        exitMenuItem.addActionListener(this);

        // Show the window
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        // If the user clicks the "New" menu item
        if (e.getSource() == newMenuItem) {
            // Clear the text area
            textArea.setText("");
        }
        // If the user clicks the "Open" menu item
        else if (e.getSource() == openMenuItem) {
            // Create a file chooser dialog
            JFileChooser fileChooser = new JFileChooser();

            // Show the dialog
            int result = fileChooser.showOpenDialog(this);

            // If the user clicks the "Open" button
            if (result == JFileChooser.APPROVE_OPTION) {
                // Get the selected file
                File file = fileChooser.getSelectedFile();

                try {
                    // Open the file and read its contents into the text area
                    BufferedReader reader = new BufferedReader(new FileReader(file));
                    String line = null;
                    while ((line = reader.readLine()) != null) {
                        textArea.append(line + "\n");
                    }
                    reader.close();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
        // If the user clicks the "Save" menu item
        else if (e.getSource() == saveMenuItem) {
            // Create a file chooser dialog
            JFileChooser fileChooser = new JFileChooser();

            // Show the dialog
            int result = fileChooser.showSaveDialog(this);

            // If the user clicks the "Save" button
            if (result == JFileChooser.APPROVE_OPTION) {
                // Get the selected file
                File file = fileChooser.getSelectedFile();

                try {
                    // Save the contents of the text area to the file
                    BufferedWriter writer = new BufferedWriter(new FileWriter(file));
                    writer.write(textArea.getText());
                    writer.close();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
        // If the user clicks the "Exit" menu item
        else if (e.getSource() == exitMenuItem) {
            // Exit the application
            System.exit(0);
        }
    }

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

这个记事本GUI包括了菜单栏和一个文本编辑区域，并且可以实现新建、打开、保存和退出功能。你可以根据自己的需求进行修改和扩展。