java简易的记事本（打开、保存、另存为、退出...）

package pay;

import java.awt.Dimension;
import java.awt.FileDialog;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;


/** 
 * @author Chase QQ: 594126573
 * @version 创建时间：2012-1-5   下午02:54:44
 * 类说明 
 */

public class TestText extends JFrame implements ActionListener{

    JMenu menu1, menu2, menu3, menu4;//菜单
    JMenuItem mt1, mt2, mt3, mt4, mt31; //子菜单
    FileDialog save, open; //保存、打开的窗口
    TextArea textArea; //文本域
    FileWriter fw;
    BufferedWriter bw;
    FileReader fr;
    BufferedReader br;
    String oldFile;
    String oldFolder;
    /**
     * 程序入口函数
     * @param args
     */
    public static void main(String[] args) {
        new TestText();
    }
    
    public TestText() {
        super("记事本");
        
        /**
         * 菜单栏
         */
        JMenuBar menuBar = new JMenuBar();
        menu1 = new JMenu("文件(F)",true);
        menu1.setMnemonic('F');
        mt1 = new JMenuItem("新建(N)",'N');
        mt1.setMnemonic('N');
        mt2 = new JMenuItem("打开(O)",'O');
        mt2.addActionListener(this);
        mt2.setMnemonic('O');
        mt3 = new JMenuItem("保存(S)",'S');
        mt3.addActionListener(this);
        mt3.setMnemonic('S');
        mt31 = new JMenuItem("另存为...");
        mt31.addActionListener(this);
        mt4 = new JMenuItem("退出(X)",'X');
        mt4.addActionListener(this);
        mt4.setMnemonic('X');
        
        menu2 = new JMenu("编辑(E)",true);
        
        
        this.setJMenuBar(menuBar);
        menuBar.add(menu1);
        menuBar.add(menu2);
        menu1.add(mt1);
        menu1.add(mt2);
        menu1.add(mt3);
        menu1.add(mt31);
        menu1.addSeparator();
        menu1.add(mt4);
        
        /**
         * 文本域
         */
        textArea = new TextArea("", 10, 10, TextArea.SCROLLBARS_VERTICAL_ONLY);
        save = new FileDialog(this, "保存文件对话框", FileDialog.SAVE);
        open = new FileDialog(this, "打开文件对话框", FileDialog.LOAD);
        
        add(textArea);
        
        Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        this.setSize(600, 600);
        this.setLocation(screenSize.width/2-this.getWidth()/2,screenSize.height/2-this.getHeight()/2);
        this.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        /**
         * 打开文件
         */
        if (e.getSource().equals(mt2)) {
            open();
        }
        /**
         * 保存文件
         */
        if (e.getSource().equals(mt3)) {
            save();
        }
        /**
         * 文件另存为
         */
        if (e.getSource().equals(mt31)) {
            saveTo();
        }
        /**
         * 退出
         */
        if (e.getSource().equals(mt4)) {
            exit();
        }
    }

    /**
     * 退出记事本
     */
    private void exit() {
        System.exit(0);
    }

    /**
     * 打开文件对话框
     */
    private void open() {
        String s;
        open.setVisible(true);
        /**
         * 打开文件
         */
        if (open.getFile() != null) {
            oldFile = open.getFile();
            oldFolder = open.getDirectory();
            File file = new File(open.getDirectory(), open.getFile());
            try {
                fr = new FileReader(file);
                String encoding = fr.getEncoding();
                InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream(file),encoding);
                br = new BufferedReader(inputStreamReader);
                textArea.setText("");
                while ((s = br.readLine())!= null) {
                    textArea.append(s + "\r\n");
                }
                fr.close();
                inputStreamReader.close();
                br.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    
    /**
     * 文件另存为
     * @throws IOException 
     */
    private void saveTo(){
        save.setVisible(true);
        /**
         * 保存文件
         */
        try {
            if (save.getFile() != null) {
                File file = new File(save.getDirectory(),save.getFile());
                fw = new FileWriter(file);
                bw = new BufferedWriter(fw);
                bw.write(textArea.getText(), 0, (textArea.getText()).length());
                bw.flush();
                bw.close();
                fw.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 保存文件
     */
    private void save() {
        String oldFile = this.oldFile;
        String oldFolder = this.oldFolder;
        if (oldFile != null && oldFolder != null) {
            File file = new File(oldFolder,oldFile);
            if (file.exists()) {
                try {
                    file.createNewFile();
                    fw = new FileWriter(file);
                    bw = new BufferedWriter(fw);
                    bw.write(textArea.getText(), 0, (textArea.getText()).length());
                    bw.flush();
                    bw.close();
                    fw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } else {
            saveTo();
        }
        
    }
}

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