Any suggestions of doing refreshing data in a web module?

Some data(xxx.txt) may be updated at some time.
I start a new thread to refresh the data.
Below is the code:

public class IPLookerServlet extends HttpServlet {
    static TreeMap<Long, String> map;

    static ExecutorService s = Executors.newSingleThreadExecutor();

    static String ipRepFile;

    static boolean isRunning = true;

    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
        System.out.println("it destroyed!!!!!!!!!!!!!!");
        isRunning = false;
        s.shutdown();
    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException
     * if an error occure
     */
    public void init() throws ServletException {
        // Put your code here
        ipRepFile = getInitParameter("ipRepFile");
        try {
            map = getIPInfo(ipRepFile);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

                s.execute(new Runnable() {
            int c = 0;

            public void run() {
                // TODO Auto-generated method stub
                while (isRunning) {
                    try {
                        Thread.sleep(1000);
                        c = (c++) % (30 * 60);//every half an hour.
                        if (c == 0) {
                            map = getIPInfo(ipRepFile);
                            System.out.println("refreshed ip repository");
                        }
                    } catch (IOException e) {
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        });
                               System.out.println("init
complete!!!!!!!!!");

    }

    private static TreeMap<Long, String> getIPInfo(String file) throws
IOException {
        TreeMap<Long, String> r = new TreeMap<Long, String>();
        BufferedReader in = new BufferedReader(new FileReader(file));
                        String buf = null;
        Pattern p = Pattern
                .compile("^(\\d+\\.\\d+\\.\\d+\\.\\d+)\\s+(\\d+\\.\\d+\\.\\d+\\.\\d
+)\\s+(.+)");
        while ((buf = in.readLine()) != null) {
            Matcher m = p.matcher(buf);
            while (m.find()) {
                long start = dealDot(m.group(1));
                r.put(start, m.group(3));
            }
        }
        in.close();
        return r;
    }
....
}