import java.awt.BorderLayout;

import java.awt.Container;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import javax.swing.JFileChooser;

import javax.swing.JFrame;

import javax.swing.JMenu;

import javax.swing.JMenuBar;

import javax.swing.JMenuItem;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

public class NotepadDemo extends JFrame implements ActionListener {

    JTextArea inputText;

    JScrollPane pane;

    public NotepadDemo() {

        this.setTitle("Notepad");

        this.setSize(600, 400);

        setLocationRelativeTo(null);

        setDefaultCloseOperation(EXIT_ON_CLOSE);

        Container contentPane = this.getContentPane();

        contentPane.setLayout(new BorderLayout(5,1));

        JMenuBar menuBar = new JMenuBar();

        JMenu menu = new JMenu("File");

        JMenuItem open=new JMenuItem("打开...");

        open.addActionListener(this);

        menu.add(open);

        JMenuItem save=new JMenuItem("存盘");

        save.addActionListener(this);

        menu.add(save);

        menu.addSeparator();

        JMenuItem item = new JMenuItem("退出");

        menu.add(item);

        item.addActionListener(this);

        menuBar.add(menu);

        this.setJMenuBar(menuBar);

        inputText=new JTextArea(100, 100);

        pane=new JScrollPane(inputText);

        contentPane.add(pane);

    }

    public static void main(String[] args) {

        JFrame frame = new NotepadDemo();

        frame.setVisible(true);

    }

    @Override

    public void actionPerformed(ActionEvent event) {

        String cmd = event.getActionCommand();

        if ("退出".equals(cmd)) {

            this.dispose();

        }

        if ("打开...".equals(cmd)) {

            File srcFile=null;

            JFileChooser fileChooser=new JFileChooser();

            int res=fileChooser.showOpenDialog(null);

            if(res==JFileChooser.APPROVE_OPTION) {

                srcFile=fileChooser.getSelectedFile();

            }

            try {

                InputStream is = new FileInputStream(srcFile);

                byte[] buffer = new byte[8*1024];

                int len;

                while ((len = is.read(buffer)) != -1) {

                    String text = new String(buffer, 0, len,"UTF-8");

                    inputText.append(text);

                }

                is.close();

            } catch (FileNotFoundException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        if ("存盘".equals(cmd)) {

            File destFile=null;

            JFileChooser fileChooser=new JFileChooser();

            int res = fileChooser.showSaveDialog(null);

            if (res == JFileChooser.APPROVE_OPTION) {

                destFile = fileChooser.getSelectedFile();

            } else {

                System.out.println("用户取消");

                return;

            }

            try {

                OutputStream os = new FileOutputStream(destFile);

                os.write(inputText.getText().getBytes("UTF-8"));

                os.close();

            } catch (FileNotFoundException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

    }

}