简单的文本编辑器。 知识点：菜单栏、快捷键、文件流、剪切板

myEditor.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.datatransfer.*;
import java.io.*;
public class myEditor extends JFrame {
    String filename;
    JTextArea tx;
    Clipboard clip = getToolkit().getSystemClipboard();
    myEditor() {
        setLayout(new GridLayout(1, 1));
        tx = new JTextArea();
        add(tx);
        JMenuBar mb = new JMenuBar();
        JMenu F = new JMenu("文件（F）");
        F.setMnemonic('F');

        JMenuItem n = new JMenuItem("新建");
        n.setAccelerator(KeyStroke.getKeyStroke('N', KeyEvent.CTRL_MASK, false));
        JMenuItem o = new JMenuItem("打开");
        o.setAccelerator(KeyStroke.getKeyStroke('O', KeyEvent.CTRL_MASK, false));
        JMenuItem s = new JMenuItem("保存");
        s.setAccelerator(KeyStroke.getKeyStroke('S', KeyEvent.CTRL_MASK, false));
        JMenuItem e = new JMenuItem("退出");
        // e.setAccelerator(KeyStroke.getKeyStroke('E',KeyEvent.CTRL_MASK,false));

        n.addActionListener(new New());
        F.add(n);
        o.addActionListener(new Open());
        F.add(o);
        s.addActionListener(new Save());
        F.add(s);
        e.addActionListener(new Exit());
        F.add(e);
        mb.add(F);
        JMenu E = new JMenu("编辑（E）");
        E.setMnemonic('E');
        JMenuItem clear = new JMenuItem("清空");
        JMenuItem cut = new JMenuItem("剪切");
        cut.setAccelerator(KeyStroke.getKeyStroke('X', KeyEvent.CTRL_MASK, false));
        JMenuItem copy = new JMenuItem("复制");
        copy.setAccelerator(KeyStroke.getKeyStroke('C', KeyEvent.CTRL_MASK, false));
        JMenuItem paste = new JMenuItem("粘贴");
        paste.setAccelerator(KeyStroke.getKeyStroke('V', KeyEvent.CTRL_MASK, false));

        clear.addActionListener(new Clear());
        E.add(clear);
        cut.addActionListener(new Cut());
        E.add(cut);
        copy.addActionListener(new Copy());
        E.add(copy);
        paste.addActionListener(new Paste());
        E.add(paste);
        mb.add(E);
        setJMenuBar(mb);

    }

    class Clear implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            tx.setText("");
        }
    }
    class New implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            tx.setText(" ");
            setTitle(filename);
        }
    }

    class Open implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            FileDialog fd = new FileDialog(myEditor.this, "请选择文件", FileDialog.LOAD);
            fd.setVisible(true);
            if (fd.getFile() != null) {
                filename = fd.getDirectory() + fd.getFile();
                setTitle(filename);
                ReadFile();
            }
            tx.requestFocus();
        }
    }

    class Save implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            FileDialog fd = new FileDialog(myEditor.this, "保存文件", FileDialog.SAVE);
            fd.setVisible(true);
            if (fd.getFile() != null) {
                filename = fd.getDirectory() + fd.getFile();
                setTitle(filename);
                try {
                    DataOutputStream d = new DataOutputStream(new FileOutputStream(filename));
                    String line = tx.getText();
                    BufferedReader br = new BufferedReader(new StringReader(line));
                    while ((line = br.readLine()) != null) {
                        d.writeBytes(line + "\r\n");
                        d.close();
                    }
                } catch (Exception ex) {
                    System.out.println("警告：找不到文件！");
                }
                tx.requestFocus();
            }
        }
    }

    class Exit implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            System.exit(0);
        }
    }
    void ReadFile() {
        BufferedReader d;
        StringBuffer sb = new StringBuffer();
        try {
            d = new BufferedReader(new FileReader(filename));
            String line;
            while ((line = d.readLine()) != null)
                sb.append(line + "\n");
            tx.setText(sb.toString());
            d.close();
        } catch (FileNotFoundException fe) {
            System.out.println("未找到文件");
        } catch (IOException ioe) {}
    }

    class Cut implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            String sel = tx.getSelectedText();
            StringSelection ss = new StringSelection(sel);
            clip.setContents(ss, ss);
            tx.replaceRange(" ", tx.getSelectionStart(), tx.getSelectionEnd());
        }
    }

    class Copy implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            String sel = tx.getSelectedText();
            StringSelection clipString = new StringSelection(sel);
            clip.setContents(clipString, clipString);
        }
    }

    class Paste implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            Transferable cliptran = clip.getContents(myEditor.this);
            try {
                String sel = (String) cliptran.getTransferData(DataFlavor.stringFlavor);
                tx.replaceRange(sel, tx.getSelectionStart(), tx.getSelectionEnd());
            } catch (Exception exc) {
                System.out.println("注意：粘贴板中无字符串内容！");
            }
        }
    }

    public static void main(String args[]) {
        Frame f = new myEditor();
        f.setSize(600, 480);
        f.setLocation(120, 80);
        f.setVisible(true);
    }
}