private void init(){
  setFocusPainted(false);
  setFocusable(false);
  JComboBox box=new JComboBox();
  Object preventHide=box.getClientProperty("doNotCancelPopup");
  putClientProperty("doNotCancelPopup",preventHide);
}

private void init ( ) { setFocusPainted ( false ) ; setFocusable ( false ) ; JComboBox box = new JComboBox ( ) ; Object preventHide = box . getClientProperty ( "doNotCancelPopup" ) ; putClientProperty ( "doNotCancelPopup" , preventHide ) ; }
initialize the column control button ' s gui
