利用Java Swing 图形组件开发一个图形化简易记事本。记事本功能包括文本编辑、保存文本到指定路径、打开指定路径下的文本、退出等。菜单中的三个选项均应能正常实现功能。

好的，以下是一个简单的Java Swing记事本的实现：

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

public class SimpleNotepad extends JFrame implements ActionListener {

    private JTextArea textArea;
    private JMenuBar menuBar;
    private JMenu fileMenu, editMenu, helpMenu;
    private JMenuItem newMenuItem, openMenuItem, saveMenuItem, exitMenuItem, cutMenuItem, copyMenuItem,
            pasteMenuItem, aboutMenuItem;

    private File file;

    public SimpleNotepad() {
        setTitle("Simple Notepad");
        setSize(600, 400);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

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

        menuBar = new JMenuBar();

        fileMenu = new JMenu("File");
        editMenu = new JMenu("Edit");
        helpMenu = new JMenu("Help");

        newMenuItem = new JMenuItem("New");
        openMenuItem = new JMenuItem("Open");
        saveMenuItem = new JMenuItem("Save");
        exitMenuItem = new JMenuItem("Exit");

        cutMenuItem = new JMenuItem("Cut");
        copyMenuItem = new JMenuItem("Copy");
        pasteMenuItem = new JMenuItem("Paste");

        aboutMenuItem = new JMenuItem("About");

        fileMenu.add(newMenuItem);
        fileMenu.add(openMenuItem);
        fileMenu.add(saveMenuItem);
        fileMenu.addSeparator();
        fileMenu.add(exitMenuItem);

        editMenu.add(cutMenuItem);
        editMenu.add(copyMenuItem);
        editMenu.add(pasteMenuItem);

        helpMenu.add(aboutMenuItem);

        menuBar.add(fileMenu);
        menuBar.add(editMenu);
        menuBar.add(helpMenu);

        setJMenuBar(menuBar);

        newMenuItem.addActionListener(this);
        openMenuItem.addActionListener(this);
        saveMenuItem.addActionListener(this);
        exitMenuItem.addActionListener(this);

        cutMenuItem.addActionListener(this);
        copyMenuItem.addActionListener(this);
        pasteMenuItem.addActionListener(this);

        aboutMenuItem.addActionListener(this);

        setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == newMenuItem) {
            textArea.setText("");
            file = null;
        } else if (e.getSource() == openMenuItem) {
            JFileChooser fileChooser = new JFileChooser();
            int result = fileChooser.showOpenDialog(this);
            if (result == JFileChooser.APPROVE_OPTION) {
                file = fileChooser.getSelectedFile();
                try {
                    BufferedReader reader = new BufferedReader(new FileReader(file));
                    String line = null;
                    while ((line = reader.readLine()) != null) {
                        textArea.append(line + "\n");
                    }
                    reader.close();
                } catch (IOException ex) {
                    JOptionPane.showMessageDialog(this, ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
                }
            }
        } else if (e.getSource() == saveMenuItem) {
            if (file == null) {
                JFileChooser fileChooser = new JFileChooser();
                int result = fileChooser.showSaveDialog(this);
                if (result == JFileChooser.APPROVE_OPTION) {
                    file = fileChooser.getSelectedFile();
                }
            }
            if (file != null) {
                try {
                    BufferedWriter writer = new BufferedWriter(new FileWriter(file));
                    writer.write(textArea.getText());
                    writer.close();
                } catch (IOException ex) {
                    JOptionPane.showMessageDialog(this, ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
                }
            }
        } else if (e.getSource() == exitMenuItem) {
            System.exit(0);
        } else if (e.getSource() == cutMenuItem) {
            textArea.cut();
        } else if (e.getSource() == copyMenuItem) {
            textArea.copy();
        } else if (e.getSource() == pasteMenuItem) {
            textArea.paste();
        } else if (e.getSource() == aboutMenuItem) {
            JOptionPane.showMessageDialog(this, "Simple Notepad v1.0", "About", JOptionPane.INFORMATION_MESSAGE);
        }
    }

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

这个记事本可以进行文本编辑、保存文本到指定路径、打开指定路径下的文本、退出等功能。通过菜单的选项可以实现这些功能。