近來上課想做一個隨機點名的小軟體，剛剛寫了一個，望大家指正。

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.util.List;
import java.util.ArrayList;

public class DianName extends Frame{
	
	private String fileName="a.txt";
	private File f;
	private FileReader fr;
	private BufferedReader br;
	private List<String> names=new ArrayList<String>();
	private String strName;
	
	private Label labelName;
	private Button btOK;
	
	public static void main(String[] args){
		DianName dn=new DianName();
		dn.newFrame();
		dn.read();
	}
	
	public void newFrame(){
		labelName=new Label("顯示姓名");
		btOK=new Button("開始");
		
		this.setLocation(300,300);
		this.setResizable(false);
		this.setSize(500,400);
		this.add(labelName,BorderLayout.NORTH);
		this.add(btOK,BorderLayout.SOUTH);
		this.pack();
		this.setVisible(true);
		this.addWindowListener(new WindowAdapter(){
			public void windowClosing(WindowEvent e){
				System.exit(0);
			}
		});
		btOK.addActionListener(new ButtonAction());
	}
	
	public void read(){
		try{
			f=new File(fileName);
			if(!f.exists()){
				f.createNewFile();
			}
			fr=new FileReader(f);
			br=new BufferedReader(fr);
			String str=br.readLine();
			while(str!=null){
				names.add(str);
				str=br.readLine();
			}
		}catch(Exception e){
			e.printStackTrace();
		}
		
	}
	
	public void write(){
		try{
			int index=(int)(Math.random()*names.size());
			strName=names.get(index);
		}catch(Exception e){
			e.printStackTrace();
		}
		
	}
	
	private class ButtonAction implements ActionListener{
		public void actionPerformed(ActionEvent e){
			write();
			labelName.setText(strName);
		}
	}
}