title: Constantly checking a boolean value
body: <p>I have 2 classes. The first class turns a boolean value to true when you click on a specific location, the second class calls    <code>frame.removeAll()</code> and    <code>frame.add(new CanvasSelect())</code> If the boolean in the first class is true.  It seems to only check the boolean value once.</p>
  
  <p>Is there any way to make the second class constantly check the boolean value in the first class?</p>