this. addListener ( new Listener ( ) {
    @EventHandler
    public void onPreSell (AuctionPreSellEvent event ) {
       
        System. out. println (event. getItemStack ( ) ) ;
        System. out. println (event. getPrice ( ) ) ;
        System. out. println (event. getEconomy ( ). name ( ) ) ;
       
        event. setItemStack ( new ItemStack (Material. DIAMOND, event. getAmount ( ) ) ) ;
    }
} ) ;