ZK - add onCheck event to ZK Checkbox component using JAVA

add onCheck event to ZK Checkbox  component using JAVA
private Grid           listGrid;

 Checkbox checkbox = new Checkbox();
        checkbox.setValue("value");
        //checkbox.addForward(Events.ON_CHECK, "onModifySelectedList", null);
        checkbox.addEventListener(Events.ON_CHECK, new EventListener()
        {
          public void onEvent( Event arg0 ) throws Exception
          {

            onModifySelectedList(arg0);
          }
        });

  public void onModifySelectedList( Event event )
  {
    Checkbox checkbox = (Checkbox)event.getTarget();
    if (checkbox.isChecked())
    {
      System.out.println("check box is checked");
    }
    else
    {
      System.out.println("check box is unchecked");
     }

     }