title: Check if a stage is already open before open it again javafx
body: <p>I'm trying to open  a stage by clicking a button, but before opening it, I want to check if the stage is already opened, then popup the opened stage to the front instead of opening a new one(no multi open of the same Stage). </p>
  
  <pre><code>@FXML
  private void btn_Validate(ActionEvent event) {
  
      try {
          FXMLLoader loader = new FXMLLoader(getClass().getResource("/scontrols/students/StudentManagement.fxml"));
          Parent root = (Parent) loader.load();
  
          StudentManagementController sendTo =  loader.getController();
          sendTo.receiveFromCamera(txtPictureName.getText());
          Stage stage = new Stage();
          stage.setScene(new Scene(root));
           if(!stage.isShowing())
           {
               stage.show();}
  
      } catch (IOException ex) {
          Logger.getLogger(WebCamController.class.getName()).log(Level.SEVERE, null, ex);
      }
  }
  </code></pre>