title: How to disable (or hide) the close (x) button on a JFrame?
body: <p>I have a window (derived from JFrame) and I want to disable the close button during certain operations which are not interruptible.  I know I can make the button not do anything (or call a handler in a WindowListener) by calling</p>
  
  <pre><code>setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
  </code></pre>
  
  <p>but I would like to make it clear visually that it is pointless to click it.</p>