关于java数据流的应运小练习 有图有代码

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上面为效果图：

下面为代码：

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;

import javax.swing.JButton;
import javax.swing.JEditorPane;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;

import org.omg.CORBA.portable.OutputStream;

public class File_sava_open extends JFrame implements ActionListener {

 /**
  * @param args
  */
 JPanel jp;
 JButton jb1, jb2, jb3;
 JEditorPane jep;
    
 JFileChooser jfc;

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  File_sava_open mh = new File_sava_open();
 }

 public File_sava_open() {
  // 定义一个JP
  jp = new JPanel();
  jep = new JEditorPane();
  jb1 = new JButton("打开");
  jb1.setActionCommand("dk");
  jb1.addActionListener(this);
  jb2 = new JButton("保存");
  jb2.setActionCommand("bc");
  jb2.addActionListener(this);
  jb3 = new JButton("取消");
  // 添加组件
  jp.add(jb1);
  jp.add(jb2);
  jp.add(jb3);
  this.add(jep);
  this.add(jp, "South");
  // 设置界面
  this.setLocation(300, 200);
  this.setTitle("记事本");
  this.setSize(300, 400);
  this.setVisible(true);

 }

 @Override
 public void actionPerformed(ActionEvent arg0) {
  // TODO Auto-generated method stub
  //响应打开按钮  并显示所选文件内容
  if (arg0.getActionCommand().equals("dk")) {
   System.out.println();
   jfc = new JFileChooser();
   int returnval = jfc.showOpenDialog(this);
   if (returnval == jfc.APPROVE_OPTION) {
    String filename = jfc.getSelectedFile().getAbsolutePath();
    try {
     InputStream is = new FileInputStream(filename);
     BufferedInputStream bis=new BufferedInputStream(is);
     byte[] by = new byte[is.available()];
     bis.read(by);
     String str = new String(by);
     jep.setText(str);
     bis.close();

    } catch (Exception e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }

   }

  }
  if (arg0.getActionCommand().equals("bc")) {
   //响应保存按钮  并显示所选文件内容
   System.out.println();
   jfc = new JFileChooser();
   int m = jfc.showSaveDialog(this);
   if (m == jfc.APPROVE_OPTION) {
    String filename = jfc.getSelectedFile().getAbsolutePath();
    try {
     
     FileOutputStream os = new FileOutputStream(filename,true);
     BufferedOutputStream bos=new BufferedOutputStream(os);
     String str=jep.getText();
     bos.write(str.getBytes());
     bos.close();
    } catch (Exception e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }

   }

  }
 }
}