利用JFileChooser实现文件选择对话框

package mypackage;
/**
 * 文件过滤
 */
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.filechooser.FileFilter;

public class FileFilterUtils implements ActionListener{
 
 JFrame f = null;
 JLabel label = null;
 JFileChooser fileChooser = null;
 
 public FileFilterUtils() {
  f= new JFrame("FileFilter");
  Container contentPane = f.getContentPane();
  
  JButton b = new JButton("打开文件");
  
  b.addActionListener(this);
  
  label = new JLabel(" ",JLabel.CENTER);
  label.setPreferredSize(new Dimension(150, 30));
  contentPane.add(label,BorderLayout.CENTER);
  contentPane.add(b,BorderLayout.SOUTH);
  
  f.pack();
  f.setVisible(true);
  f.addWindowListener(new WindowListener() {
   
   @Override
   public void windowOpened(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
   
   @Override
   public void windowIconified(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
   
   @Override
   public void windowDeiconified(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
   
   @Override
   public void windowDeactivated(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
   
   @Override
   public void windowClosing(WindowEvent e) {
    System.exit(0);
    
   }
   
   @Override
   public void windowClosed(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
   
   @Override
   public void windowActivated(WindowEvent e) {
    // TODO Auto-generated method stub
    
   }
  });
 }
 
 public static void main(String[] args) {
  new FileFilterUtils();

 }
 
 public void actionPerformed(ActionEvent e) {
  fileChooser = new JFileChooser("c:\\");
  fileChooser.addChoosableFileFilter(new JAVAFileFilter("class"));
  fileChooser.addChoosableFileFilter(new JAVAFileFilter("java"));
  int result = fileChooser.showOpenDialog(f);
  if(result == JFileChooser.APPROVE_OPTION) {
   File file = fileChooser.getSelectedFile();
   label.setText("您选择了："+file.getName()+"文件");
  }else if(result == fileChooser.CANCEL_OPTION) {
   label.setText("您没有选取文件");
  }
 }
}
 class JAVAFileFilter extends FileFilter{
  String ext;
  
  public JAVAFileFilter(String ext) {
   this.ext = ext;
  }
  
  public boolean accept(File file) {
   if(file.isDirectory())
    return true;
   
   String fileName = file.getName();
   int index = fileName.lastIndexOf(‘.‘);
   if(index > 0&& index<fileName.length()-1) {
    String extension = fileName.substring(index+1).toLowerCase();
    if(extension.equals(ext))
     return true;
   }
   return false;
  }
  
  public String getDescription() {
   if(ext.equals("java"))
    return "JAVA Source File (*.java)";
   if(ext.equals("class"))
    return "JAVA Source File (*.class)";
   return "";
  }
 }