Enlist soldiers and generals, draw small programs, multi-threaded display time

package pointSoldierPoint;

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import java.util.TreeSet;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.xml.crypto.Data;

/** 
* @author : htf 
*   Java The program for ordering soldiers and generals , Luck draw , Time stamp 
*/
public class Soldier extends JFrame implements Runnable{

	/**
	 *  Declare five components ：Frame  Panel  Button  Label  TextArea
	 */
	private JPanel panel;
	private JButton button;
	private JLabel label;
	private JTextArea text;
	
	/**
	 * data source 
	 */
	private static Map<Integer, String> map=null;
	
	
	static {
		map=new HashMap<Integer, String>();
		String name=null;
		int id=1;	
		
		// Get files from outside 
		File file=new File("students.txt");
		try(BufferedReader bf=new BufferedReader(new FileReader(file));){
			while((name=bf.readLine())!=null) {
				map.put(id, name);
				id++;
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	// Call other methods by constructing methods , And set the relevant properties 
	public Soldier() {
		init();
		buttonAt();
		this.setSize(600, 500);// Form size 
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);// close 
		this.setTitle(" Luck draw ");// title 
		this.setVisible(true);// Set display 
	}
	/**
	 *  Instantiate objects    init, Assembly components 
	 */
	public void init() {
		
		panel=new JPanel(new GridLayout(3, 1));// Grid layout 
		button=new JButton(" Am I ");
		label=new JLabel(" The winners ");
		text=new JTextArea(3,30);
		
		panel.add(button);
		panel.add(label);
		panel.add(text);
		
		this.getContentPane().add(panel);
		
	}
	
	/**
	 *  Register listener 
	 *  Generate random numbers , obtain map,key Value corresponds to information , Show it to the program 
	 */
	public void buttonAt() {
		button.addActionListener((e)->{
			
			TreeSet<Integer> set=new TreeSet<>();// Sorting is not repeated 
			while(set.size()<5) {
				Random random=new Random();
				int num=random.nextInt(29)+1;
				set.add(num);
			}
			StringBuffer sb =new StringBuffer();// Store the name of the winner 
			
			for(Integer s:set) {
				String name=map.get(s);
				sb.append(name+",");
			}
			text.setText(sb.substring(0, sb.toString().length()-1));
		});
	}
	public static void main(String[] args) {
		System.out.println(map.size());
		Soldier s1=new Soldier();// Construction method 
		new Thread(s1).start();// Start time thread 
	}
	@Override
	public void run() {
		// TODO Auto-generated method stub
		// Setup time 
		while(true) {
			Date date=new Date();
			SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
			String time =sdf.format(date);
			label.setText(" The winners ( current time "+time+")");
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			
		}
	}
}