Java作业5

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