title: How to check whether a radiobutton is selected in a buttongroup?
body: <p>I have a buttongroup of 5 radio buttons and I need to check if at least one of them is selected or not.</p>
  
  <p>Is this right?</p>
  
  <p><code>buttonGroup1.isSelected(ButtonModel);</code></p>
  
  <p>But what is <code>ButtonmModel</code> here?</p>