title: How to create a popup window in javafx
body: <p>I want to create a popup window in a JavaFX application. Give me some ideas.</p>
  <p><img src="https://i.stack.imgur.com/0s8w8.png" alt="enter image description here" /></p>
  <p>When I click on <em>Check</em> button it opens the popup window.
  How to do it?</p>