Java Test

简易记事本

package Test;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;

public class Jishiben implements ActionListener {
    private Frame frame;
    private  FileDialog fd_load;
    private  FileDialog fd_save;
    private  TextArea ta;
    private  String file="";
    private  MenuItem save;
    private RandomAccessFile raf;
    private FileChannel fci;
    private FileLock flock;
    private CharsetEncoder encoder;
    private CharsetDecoder decoder;

    public static void main(String[] args) {
        new Jishiben().init();
    }
    public void init(){
        frame=new Frame("我的笔记本");
        MenuBar mb=new MenuBar();
        Menu file=new Menu("file");
        Menu help=new Menu("help");
        MenuItem open=new MenuItem("open");
        save=new MenuItem("save");
        save.setEnabled(false);
        file.add(open);
        file.add(save);
        mb.add(file);
        mb.add(help);
        frame.setMenuBar(mb);
        ta=new TextArea();
        frame.add(ta,"Center");
        open.addActionListener(this);
        save.addActionListener(this);
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        frame.setSize(600,400);
        frame.setLocation(300,100);
        frame.setVisible(true);
        fd_load=new FileDialog(frame,"打开文件",FileDialog.LOAD);
        fd_save=new FileDialog(frame,"保存文件",FileDialog.SAVE);
        Charset charset=Charset.forName(System.getProperty("file.encoding"));
        encoder= charset.newEncoder();
        decoder= charset.newDecoder();

    }
    public void actionPerformed(ActionEvent e){
        String s=e.getActionCommand();
        if (s.equals("open")){
            fd_load.setVisible(true);
            String d=fd_load.getDirectory();
            String f=fd_load.getFile();
            if ((d!=null)&&(f!=null)){
                String destfile=d+f;
                if (destfile.equals(file)){
                    return;
                }else {
                    this.closeFile();
                    file=destfile;
                    this.loadFile();
                }

            }
        }else if (s.equals("save")){
            this.saveFile();
        }
    }

    private void saveFile() {
        String content= ta.getText();
        try{
            CharBuffer cb=CharBuffer.wrap(content.toCharArray());
            ByteBuffer bb=encoder.encode(cb);
            raf.setLength(0);
            fci.write(bb);
            fci.force(true);
        }catch (IOException e){
            e.printStackTrace();
        }
    }

    private void loadFile() {
        try{
            raf=new RandomAccessFile(file,"rw");
            fci=raf.getChannel();
            flock=fci.tryLock();
            if (flock==null){
                ta.setText("");
                JOptionPane.showMessageDialog(null,"文件正在使用中喔","错误提示",JOptionPane.ERROR_MESSAGE);
                file="";
                raf.close();
                raf=null;
            }else {
                int length=(int)fci.size();
                ByteBuffer bb=ByteBuffer.allocate(length);
                fci.read(bb);
                bb.flip();
                CharBuffer cb=decoder.decode(bb);
                ta.setText(cb.toString());
                frame.setTitle("我的笔记本"+file);
                save.setEnabled(true);

            }
        }catch(IOException e){
            e.printStackTrace();
        }
    }

    private void closeFile() {
        try{
            if (flock!=null){
                flock.release();
            }
            if (raf!=null){
                raf.close();
            }
            file="";
            frame.setTitle("我的记事本");
            save.setEnabled(false);
        }catch(IOException e){
            e.printStackTrace();
        }
    }
}