Crie um inventário para confirmar a ação de um player, utilizando o pattern builder

Confirmar.java

import com.dont.empregos.Terminal;
import org.bukkit.Bukkit;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.inventory.InventoryClickEvent;
import org.bukkit.inventory.Inventory;
import org.bukkit.inventory.InventoryHolder;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;

import java.util.function.Consumer;

/**
 author: dont
 */

public class Confirmar {

    static {
        Bukkit.getPluginManager().registerEvents(new Listener() {
            @EventHandler
            public void onClick(InventoryClickEvent e){
                if (e.getInventory().getHolder() instanceof ConfirmarHolder){
                    e.setCancelled(true);
                    ConfirmarHolder holder = (ConfirmarHolder) e.getInventory().getHolder();
                    Player player = (Player) e.getWhoClicked();
                    if (holder.get().getConfirmarSlot() == e.getSlot()){
                        player.closeInventory();
                        holder.get().getOnConfirmar().accept(player);
                    } else if (holder.get().getRecusarSlot() == e.getSlot()){
                        player.closeInventory();
                        holder.get().getOnRecusar().accept(player);
                    }
                }
            }
        }, Terminal.getPlugin(Terminal.class)); //sua main
    }

    private Consumer<Player> recusar, confirmar;
    private ItemStack middleItem;
    private int recusarSlot, confirmarSlot, middleSlot;
    private Inventory inventory;

    public Confirmar(Builder builder) {
        this.recusar = builder.recusar;
        this.confirmar = builder.confirmar;
        this.middleItem = builder.middleItem;
        this.recusarSlot = builder.recusarSlot;
        this.confirmarSlot = builder.confirmarSlot;
        this.middleSlot = builder.middleSlot;
        createInventory();
    }

    private void createInventory(){
        inventory = Bukkit.createInventory(new ConfirmarHolder(this), 27, "Confirmar");
        inventory.setItem(middleSlot, middleItem);
        inventory.setItem(recusarSlot, createItem("§cCancelar",14));
        inventory.setItem(confirmarSlot, createItem("§aConfirmar",5));
    }

    private ItemStack createItem(String name, int durability){
        ItemStack item = new ItemStack(Material.STAINED_CLAY, 1, (short) durability);
        ItemMeta meta = item.getItemMeta();
        meta.setDisplayName(name);
        item.setItemMeta(meta);
        return item;
    }

    public void open(Player player){
        player.openInventory(inventory);
    }

    public int getRecusarSlot() {
        return recusarSlot;
    }

    public int getConfirmarSlot() {
        return confirmarSlot;
    }

    public Consumer<Player> getOnRecusar() {
        return recusar;
    }

    public Consumer<Player> getOnConfirmar() {
        return confirmar;
    }

    public class ConfirmarHolder implements InventoryHolder {

        private Confirmar confirmar;

        public ConfirmarHolder(Confirmar confirmar) {
            this.confirmar = confirmar;
        }

        public Confirmar get() {
            return confirmar;
        }

        @Override
        public Inventory getInventory() {
            return null;
        }
    }

    public static class Builder {

        private Consumer<Player> recusar, confirmar;
        private ItemStack middleItem;
        private int recusarSlot, confirmarSlot, middleSlot;

        public Builder() {
            recusar = p -> {};
            confirmar = p -> {};
            middleItem = new ItemStack(Material.AIR);
            recusarSlot = 11;
            middleSlot = 13;
            confirmarSlot = 15;
        }

        public Builder onRecusar(Consumer<Player> recusar){
            this.recusar = recusar;
            return this;
        }

        public Builder onConfirmar(Consumer<Player> confirmar){
            this.confirmar = confirmar;
            return this;
        }

        public Builder withMiddleItem(ItemStack middleItem){
            this.middleItem = middleItem;
            return this;
        }

        public Builder withSlots(int recusarSlot, int confirmarSlot, int middleSlot){
            this.recusarSlot = recusarSlot;
            this.confirmarSlot = confirmarSlot;
            this.middleSlot = middleSlot;
            return this;
        }

        public Confirmar build(){
            return new Confirmar(this);
        }

    }

}

ConfirmarExemplo.java

// exemplo real de uso
private final Confirmar QUIT = new Confirmar.Builder().onConfirmar(player -> {
        User user = (User) manager.cache.get(player.getName());
        user.setEmpregoAtual(null);
        user.setLastChange(System.currentTimeMillis());
        player.sendMessage("§eVocê saiu do emprego com sucesso.");
        player.playSound(player.getLocation(), Sound.ORB_PICKUP, 1, 1);
        main.getEmpregoManager().open(player); //abre o menu de empregos de volta
    }).onRecusar(player -> {
        main.getEmpregoManager().open(player); //abre o menu de empregos de volta
    }).build();

    @EventHandler
    public void onClick(InventoryClickEvent e){
        if (e.getInventory().getName().equals("Empregos")){
            e.setCancelled(true);
            Player player = (Player) e.getWhoClicked();
            User user = (User) manager.cache.get(player.getName());

            if (e.getSlot() == 8){
                if (user.getEmpregoAtual() == null){
                    player.sendMessage("§eVocê já está desempregado.");
                    player.playSound(player.getLocation(), Sound.VILLAGER_NO, 1, 1);
                    return;
                }
                QUIT.open(player);
            }
        }
    }