question: private void updateIndexColumnButtons ( ) { indexRemoveButton . setEnabled ( false ) ; indexUpButton . setEnabled ( false ) ; indexDownButton . setEnabled ( false ) ; int index = selectedColumns . getSelectionIndex ( ) ; if ( index >= 0 ) { indexRemoveButton . setEnabled ( true ) ; if ( index > 0 ) { indexUpButton . setEnabled ( true ) ; } else if ( index < selectedColumns . getItemCount ( ) - 1 ) { indexDownButton . setEnabled ( true ) ; } } }
target:  Updates status of index column up / down buttons.