Java第五次实验

import javax.swing.*;
import java.awt.*;
import java.io.File;

public class ListFilesUI extends JFrame{

    public static String listDirectory(File dir) throws IllegalAccessException{
        if(!dir.exists()){
            throw new IllegalAccessException("目录"+dir+"不存在");
        }
        if(!dir.isDirectory()){
            //判断是不是目录
            throw new IllegalArgumentException(dir+"不是目录");
        }
        String[] fileName = dir.list();    
        String name ="";
        for(String a : fileName){
            name=name+a+"\n";}
        return name;
        }
    
    public static void main(String[] args) {
        JFrame frame=new JFrame();
        JPanel main_panel =new JPanel(new BorderLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //frame.setLayout(null);
        String[] itme =new String[]{"all",".doc"};
        JComboBox box=new JComboBox();
        for(int i=0;i<itme.length;i++){
            box.addItem(itme[i]);
        }
        box.setEnabled(true);
        box.setEditable(true);
        box.setMaximumRowCount(6);
        box.setBounds(230,30,130,25);
        frame.setBounds(400,300,400,200);
        frame.setVisible(true);
        JTextArea main_text =new JTextArea();
         main_text.setBackground(Color.BLACK);
        JScrollPane AA=new JScrollPane();
        AA.setViewportView(main_text);
        main_text.setEnabled(false);
        main_panel.add(box,BorderLayout.NORTH);
        main_panel.add(AA,BorderLayout.CENTER);
        frame.add(main_panel);
        
        try {
            String str=ListFilesUI.listDirectory(new File("C:\\Users\\Administrator\\Desktop\\Java作业5"));
            main_text.setText(str);
        }
        catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        frame.setBounds(400,200,400,200);
        frame.setVisible(true);

    }
}

结果截图：