title: Notification popup doesn't run with single instance
body: <p>I want to display notification pop up when user attempts to run  application second time , So I create NotificationPop  obj and call the method to display the dialog within my single instance class ,but , it doesn't display popup when application runs second time  there is no problem with my NotificationPop window it functions normal however when I call  it within Single Instance doesn't display. in output window of Netbeans it displays dialog is closed as well. Do i miss any step here ?  </p>
  
  <pre><code>import java.io.File;
  import java.io.IOException;
  import java.io.RandomAccessFile;
  import java.nio.channels.FileChannel;
  import java.nio.channels.FileLock;
  
  public class SingleInstance {
  
      public static File f;
      public static FileChannel channel;
      public static FileLock lock;
      public static TrayCon trayobj;
      public static boolean checkstatus;
      public static NotificationPop obj;
  
      public static void main(String args[]) throws IOException {
          try {
              f = new File("key");
              if (f.exists()) {
                  f.delete();
              }
              channel = new RandomAccessFile(f, "rw").getChannel();
              lock = channel.tryLock();
              if (lock == null) {
                  obj = new NotificationPop();
                  obj.displaypopupmessage();
                  System.exit(0);
                  channel.close();
                  throw new RuntimeException("Only 1 instance can run");
              }
  
              java.awt.EventQueue.invokeLater(new Runnable() {
                  public void run() {
  
                      trayobj = new TrayCon();
                      trayobj.CreateTrayCon(trayobj);
                  }
              });
  
          } catch (IOException ex) {
          }
      }
  }
  </code></pre>