appendio.java

java 基础的 一点东西,,可以看看

import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;

class AppendIO extends JFrame implements ActionListener {
   JLabel text;
   JButton button;
   JPanel panel;
   JTextField textField;
   private boolean _clickMeMode = true;

   AppendIO() { //Begin Constructor
     text = new JLabel("Text to save to file:");
     button = new JButton("Click Me");
     button.addActionListener(this);
     textField = new JTextField(30);
     panel = new JPanel();
     panel.setLayout(new BorderLayout());
     panel.setBackground(Color.white);
     getContentPane().add(panel);
     panel.add(BorderLayout.NORTH, text);
     panel.add(BorderLayout.CENTER, textField);
     panel.add(BorderLayout.SOUTH, button);
   } //End Constructor

   public void actionPerformed(ActionEvent event){
     Object source = event.getSource();
     if (source == button){
       String s = null;
       if (_clickMeMode){
         try {
      //Write to file
          String text = textField.getText();
          byte b[] = text.getBytes();
          String outputFileName = System.getProperty("user.home",
                                File.separatorChar + "home" + 
                                File.separatorChar + "zelda") + 
                                File.separatorChar + "text.txt";
          File outputFile = new File(outputFileName);
          RandomAccessFile out = new RandomAccessFile(outputFile, "rw");
          out.seek(outputFile.length());
          out.write(b);

     //Write a new line (NL) to the file.
         out.writeByte('\n');
         out.close();

    //Read from file
         String inputFileName = System.getProperty("user.home",
                             File.separatorChar + "home" + 
                             File.separatorChar + "zelda") + 
                             File.separatorChar + "text.txt";
         File inputFile = new File(inputFileName);
         FileInputStream in = new FileInputStream(inputFile);
         byte bt[] = new byte[(int)inputFile.length()];
         in.read(bt);
         s = new String(bt);
         in.close();
       } catch(java.io.IOException e) {
         System.out.println(e.toString());
       }
//Clear text field
       textField.setText("");
//Display text read from file
        text.setText("Text retrieved from file:");
        textField.setText(s);
        button.setText("Click Again");
        _clickMeMode = false;
      } else {
//Save text to file
        text.setText("Text to save to file:");
        textField.setText("");
        button.setText("Click Me");
        _clickMeMode = true;
      }
   }
 }//end action performed method

 public static void main(String[] args) {
   JFrame frame = new AppendIO();
   frame.setTitle("Example");
   WindowListener l = new WindowAdapter() {
   public void windowClosing(WindowEvent e) {
       System.exit(0);
     }
   };
   frame.addWindowListener(l);
   frame.pack();
   frame.setVisible(true);
  }
}