fileio.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 FileIO extends JFrame implements ActionListener {
   JLabel text;
   JButton button;
   JPanel panel;
   JTextField textField;
   private boolean _clickMeMode = true;

   FileIO() { //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();
//The equals operator (==) is one of the few operators
//allowed on an object in the Java programming language
     if (source == button) {
       String s = null;
       //Write to file
       if (_clickMeMode){
         try {
          String text = textField.getText();
          byte b[] = text.getBytes();
          String outputFileName = System.getProperty("user.home",
                                File.separatorChar + "home" + 
                                File.separatorChar + "zelda") + 
                                File.separatorChar + "text.txt";
          FileOutputStream out = new FileOutputStream(outputFileName);
          out.write(b);
          out.close();
         } catch(java.io.IOException e) {
           System.out.println("Cannot write to text.txt");
         }
      //Read from file
          try {
          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("Cannot read from text.txt");
          }
        //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;
        }
    }
 }

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