DispenserBlocker SelectionListener

package DispenserBlocker.Listeners;

import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.block.Action;
import org.bukkit.event.block.BlockDispenseEvent;
import org.bukkit.event.entity.ItemSpawnEvent;

public class SelectionListener implements Listener {

    @EventHandler
    public void onDispense(BlockDispenseEvent event){

        if (!(event.getItem().getType() == Material.EMERALD)){

            if(){
                event.setCancelled(true);
            }

        }
        if (!(event.getItem().getType() == Material.GOLD_NUGGET)){

            if(){
                event.setCancelled(true);
            }
        }


    }