title: How to check if JDialog is already opened in Java?
body: <p>I am currently developing a digital clock widget. I have designed it using a <strong>JPanel form</strong> and add it to a <strong>JDialog</strong>. Here is the code.</p>
  
  <pre><code>static JDialog jDialog = new JDialog();
  
  public static void main(String[] args)
  {
     jDialog.setUndecorated(true);
     jDialog.add(new QuickLauncher());
     jDialog.pack();
     jDialog.setBackground(new Color(0, 255, 0, 0));
     jDialog.setLocationRelativeTo(null);
     jDialog.setVisible(true);
   }
  </code></pre>
  
  <p>The problem is when I run this program twice it opens two windows. So what I need is I need only one window to run and if I run the program again instead of running the program again, it needs to focus the application. I tried various examples and methods like <code>isVisible()</code> and <code>isActive()</code> but I can't figure it out how to fix this issue. I tried this also,</p>
  
  <p><a href="https://stackoverflow.com/questions/17397442/how-to-check-if-a-jframe-is-opened">How to check if a jframe is opened?</a></p>
  
  <p>Please anyone can help me? Thanks in advance.</p>