java 模拟实现记事本功能代码

以下是一个简单的 Java 记事本程序，它具有基本的文本编辑和保存功能：

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

public class Notepad extends Frame implements ActionListener {
    private TextArea textArea = new TextArea("", 0,0, TextArea.SCROLLBARS_VERTICAL_ONLY);
    private MenuBar menuBar = new MenuBar(); // first, create a MenuBar item
    private Menu file = new Menu(); // our File menu
    // what's going in File? let's see...
    private MenuItem openFile = new MenuItem(); // an open option
    private MenuItem saveFile = new MenuItem(); // a save option
    private MenuItem close = new MenuItem(); // and a close option!

    public Notepad() {
        this.setSize(500, 300); // set the initial size of the window
        this.setTitle("Java Notepad Tutorial"); // set the title of the window
        setDefaultCloseOperation(EXIT_ON_CLOSE); // set the default close operation (exit when it gets closed)
        this.textArea.setFont(new Font("Century Gothic", Font.BOLD, 12)); // set a default font for the TextArea
        // this is why we didn't have to worry about the size of the TextArea!
        this.getContentPane().setLayout(new BorderLayout()); // the BorderLayout bit makes it fill it automatically
        this.getContentPane().add(textArea);

        // add our menu bar into the GUI
        this.setMenuBar(this.menuBar);
        this.menuBar.add(this.file); // we'll configure this later

        // first off, the design of the menuBar itself. Pretty simple, all we need to do
        // is add a few menus, which will be populated later on
        this.file.setLabel("File");

        // now it's time to work on the content of the File menu, which is simple
        // because we only need to add three things to it: an Open option, a Save option
        // and a Close option
        this.openFile.setLabel("Open");
        this.openFile.addActionListener(this); // addActionListener attaches an ActionListener to the MenuItem
        this.openFile.setShortcut(new MenuShortcut(KeyEvent.VK_O, false)); // set the keyboard shortcut
        this.file.add(this.openFile); // add it to the "File" menu

        this.saveFile.setLabel("Save");
        this.saveFile.addActionListener(this);
        this.saveFile.setShortcut(new MenuShortcut(KeyEvent.VK_S, false));
        this.file.add(this.saveFile);

        this.close.setLabel("Close");
        // along with our "CTRL+F4" shortcut to close the window, we also have
        // the default closer, as stated at the beginning of this tutorial.
        // this means that we actually have TWO shortcuts to close:
        // 1) the default close operation (example, Alt+F4 on Windows)
        // 2) CTRL+F4, which we are about to define now: (this one will appear in the label)
        this.close.setShortcut(new MenuShortcut(KeyEvent.VK_F4, false));
        this.close.addActionListener(this);
        this.file.add(this.close);
    }

    public void actionPerformed (ActionEvent e) {
        // if the source of the event was our "close" option
        if (e.getSource() == this.close)
            this.dispose(); // dispose all resources and close the application

        // if the source was the "open" option
        else if (e.getSource() == this.openFile) {
            JFileChooser open = new JFileChooser(); // open up a file chooser (a dialog for the user to browse files to open)
            int option = open.showOpenDialog(this); // get the option that the user selected (approve or cancel)
            // NOTE: because we are OPENing a file, we call showOpenDialog~
            // if the user clicked OK, we have "APPROVE_OPTION"
            // so we want to open the file
            if (option == JFileChooser.APPROVE_OPTION) {
                this.textArea.setText(""); // clear the TextArea before applying the file contents
                try {
                    // create a scanner to read the file (getSelectedFile().getPath() will get the path to the file)
                    Scanner scan = new Scanner(new FileReader(open.getSelectedFile().getPath()));
                    while (scan.hasNext()) // while there's still something to read
                        this.textArea.append(scan.nextLine() + "\n"); // append the line to the TextArea
                } catch (Exception ex) { // catch any exceptions, and...
                    // ...write to the debug console
                    System.out.println(ex.getMessage());
                }
            }
        }

        // and lastly, if the source of the event was the "save" option
        else if (e.getSource() == this.saveFile) {
            JFileChooser save = new JFileChooser(); // again, open a file chooser
            int option = save.showSaveDialog(this); // similar to the open file, only this time we call
            // showSaveDialog instead of showOpenDialog
            // if the user clicked OK (and not cancel)
            if (option == JFileChooser.APPROVE_OPTION) {
                try {
                    // create a buffered writer to write to a file
                    BufferedWriter out = new BufferedWriter(new FileWriter(save.getSelectedFile().getPath()));
                    out.write(this.textArea.getText()); // write the contents of the TextArea to the file
                    out.close(); // close the file stream
                } catch (Exception ex) { // again, catch any exceptions and...
                    // ...write to the debug console
                    System.out.println(ex.getMessage());
                }
            }
        }
    }

    // the main method, for actually creating our notepad and setting it to visible.
    public static void main(String[] args) {
        Notepad app = new Notepad();
        app.setVisible(true);
    }
}

这个程序使用了 AWT 组件，它提供了一个基本的 GUI 界面，其中包含了一个 TextArea 用于文本编辑，以及菜单栏和菜单项用于打开、保存和关闭文件。在 actionPerformed() 方法中，我们使用 JFileChooser 对话框来打开和保存文件。