JNotify

 public class JNotifySample {
   public static void main(String args[]) throws Exception {
     // path to watch
     String path ="c:/TEMP";
     // watch mask, specify events you care about,
     // or JNotify.FILE_ANY for all events.
     int mask = JNotify.FILE_CREATED |
         JNotify.FILE_DELETED |
         JNotify.FILE_MODIFIED |
        JNotify.FILE_RENAMED;

    // watch subtree?
    boolean watchSubtree = true;

    // add actual watch
    int watchID = JNotify.addWatch(path, mask, watchSubtree, new Listener());

    // sleep a little, the application will exit if you
    // don't (watching is asynchronous), depending on your
    // application, this may not be required
    Thread.sleep(1000000);

    // to remove watch the watch
    boolean res = JNotify.removeWatch(watchID);
    if (!res) {
      // invalid watch ID specified.
    }
  }

  static class Listener implements JNotifyListener {
    public void fileRenamed(int wd, String rootPath, String oldName,
        String newName) {
      print("renamed " + rootPath + " : " + oldName + " -> " + newName);
    }

    public void fileModified(int wd, String rootPath, String name) {
      print("modified " + rootPath + " : " + name);
    }

    public void fileDeleted(int wd, String rootPath, String name) {
      print("deleted " + rootPath + " : " + name);
    }

    public void fileCreated(int wd, String rootPath, String name) {
      print("created " + rootPath + " : " + name);
    }

    void print(String msg) {
      System.err.println(msg);
    }
  }
}

 public class JNotifySample2 {
   public static void main(String args[]) throws Exception {
     String path = "c:/TEMP/notify";
     int mask = JNotify.FILE_CREATED |
         JNotify.FILE_DELETED |
         JNotify.FILE_MODIFIED |
         JNotify.FILE_RENAMED;
     boolean watchSubtree = false;
     JNotify.addWatch(path, mask, watchSubtree, new JNotifyExecutorListener());
    System.out.println("Press CTR+C to stop...");
    for (; true;) {
      Thread.sleep(10000);
    }
  }
}

 package public class JNotifyExecutorListener extends JNotifyAdapter {
   volatile boolean executing = false;
   static void  p(String s){
     System.out.println(s);
   }
   @Override
   public void fileModified(int wd, String rootPath, String name) {
     p("modification is notified");
     if(!name.endsWith(".txt")){
      return;
    }
    p("executing something? "+executing);
    if (!executing) {
      p("start the BatchExecutor thread");
      Thread t = new Thread(new BatchExecutor());
      t.start();
    }
    p("modification handler method end");
  }

  class BatchExecutor implements Runnable {
    @Override
    public void run() {
      p("setting to execution...");
      // Indicating that it make no sense to
      executing = true;
      p("executing something (BatchExecutor)? "+executing);
      try {
        p("sleep a bit...");
        Thread.sleep(1 * 1000); // 1 sec
      }
      catch (InterruptedException e) {
        p(e.toString());
        return;
      }
      finally {
        p("setting back flag");
        // ready to catch the next event
        executing = false;
      }
      p("executing something (BatchExecutor 2)? "+executing);

      try {
        p("Start command line...");
        Runtime.getRuntime().exec("cmd /c Path_to/build.bat ");
      }
      catch (IOException e) {
        e.printStackTrace();
      }
      p("command is ready");
    }
  }
}