title: How to make the main GUI thread 'wait' until a separate pop-up window is disappeared
body: <p>I have an object which is invoked from the main GUI thread and shows a separate JFrame for a number of seconds and then disappear (with the use of a timer). Now I want to make the main GUI thread to wait until the pop-up JFrame window disappears. For example, on the main GUI code:</p>
  
  <pre><code>// initiate the object and show the pop-up JFrame
  DisappearingJFrame djf = new DisappearingJFrame ();
  djf.show ();
  
  // now the main GUI thread should wait
  // and after the pop-up JFrame disappears, the rest of the code is then executed
  ...
  ...
  </code></pre>
  
  <p>Any suggestion would be welcome. Thanks.</p>