public class buttplug extends JavaPlugin implements Listener {

    public void onEnable() {
        getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler(priority = EventPriority.LOWEST, ignoreCancelled = true)
    public void onPlayerDrop(PlayerDropItemEvent event) {
      if (!event.getPlayer().isOp()) {
    		event.setCancelled(true);
    	}
    }
}