import java.io.File;import java.io.IOException; public class FileUtils {	 private static String[] filenames;	 public static String fileDir(File file) throws IOException {		          if (!file.exists()) {		             System.out.println("目录不存在");		             throw new IOException();		          }		          if (!file.isDirectory()) {		              System.out.println(file + "不是目录");		              throw new IOException();		         }		          filenames = file.list();		          String mes = "";		          for (String str : filenames) {		              mes += str + '\n';		          }		        return mes;		     }	 public static String eachFileDir(String str) throws IOException {		          String mes = "";		          for (int i = 0; i < filenames.length; i++) {		              		              // 获取文件后缀名		              String postfix = filenames[i].substring(filenames[i].lastIndexOf("."));		             		              if (postfix.equalsIgnoreCase(str)) {		                  mes += filenames[i] + '\n';		              }		          }		          return mes;		      }		 }

　　此为实现调用文件功能的代码；

import java.awt.*;import java.io.File;import java.io.IOException;import javax.swing.*;public class ImageViewer {    private JTextArea list_area;    private JPanel panel;    private JFrame frame;    public ImageViewer() {        makeFrame();    }    private void makeFrame() {        frame = new JFrame("ImageViewer");        makeMenuBar();//        Container contentPane = frame.getContentPane();//        contentPane.setLayout(new BorderLayout(6, 6));        // JLabel fileLabel = new JLabel("当前还没有打开图片文件");        // JLabel statusLabel = new JLabel("ImageViewer1.0");        //        //        //        // JPanel panelW = new JPanel(new FlowLayout(FlowLayout.LEFT));        // JPanel panelInW = new JPanel(new GridLayout(2,1,2,2));        list_area= new JTextArea();        list_area.setEnabled(false);/* list_area设置不可编辑 */                try {            // 调用fileDir获取文件里面的所有文件内容            list_area.setText(FileUtils.fileDir(new File("audio")));        } catch (IOException e) {            e.printStackTrace();        }        list_area.setBackground(Color.BLACK);        panel=new JPanel(new BorderLayout());        panel.add(list_area,BorderLayout.CENTER);        frame.add(panel);        frame.setSize(260, 350);        frame.setVisible(true);    }    private void makeMenuBar() {        JMenuBar menubar = new JMenuBar();        frame.setJMenuBar(menubar);        JMenu fileMenu = new JMenu("File");        menubar.add(fileMenu);        JMenuItem openItem = new JMenuItem("OPEN");        fileMenu.add(openItem);        JMenuItem quitItem = new JMenuItem("QUIT");        fileMenu.add(quitItem);        JMenu helpMenu = new JMenu("help");        menubar.add(helpMenu);        JMenuItem aboutItem = new JMenuItem("About ImageViewer");        helpMenu.add(aboutItem);    }    public static void main(String[] args) {        // TODO Auto-generated method stub        new ImageViewer();    }}

此为GUI界面的代码并实现功能连接。其效果如下