Classe para perguntar para o jogador e retornar a resposta

ChatAsker.java

import com.dont.minas.Terminal;
import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.AsyncPlayerChatEvent;
import org.bukkit.event.player.PlayerQuitEvent;

import java.util.WeakHashMap;
import java.util.function.BiConsumer;

public class ChatAsker {

    private final static WeakHashMap<Player, ChatAsker> askers = new WeakHashMap<>();

    static {
        Terminal main = Terminal.getPlugin(Terminal.class);
        Bukkit.getPluginManager().registerEvents(new Listener() {
            @EventHandler
            public void onChat(AsyncPlayerChatEvent e) {
                ChatAsker asker = askers.get(e.getPlayer());
                if (asker != null) {
                    e.setCancelled(true);
                    BiConsumer<Player, String> consumer = asker.getOnComplete();
                    String message = e.getMessage();
                    Player player = e.getPlayer();
                    askers.remove(player);
                    consumer.accept(player, message);
                }
            }

            @EventHandler
            public void onQuit(PlayerQuitEvent e) {
                askers.remove(e.getPlayer());
            }
        }, main);
    }

    private String[] messages;
    private BiConsumer<Player, String> onComplete;

    private ChatAsker(Builder builder) {
        messages = builder.messages;
        onComplete = builder.onComplete;
    }

    public void addPlayer(Player player) {
        askers.put(player, this);
        player.sendMessage(messages);
    }

    public BiConsumer<Player, String> getOnComplete() {
        return onComplete;
    }

    public String[] getMessages() {
        return messages;
    }

    public static Builder builder() {
        return new Builder();
    }


    public static final class Builder {
        private String[] messages;
        private BiConsumer<Player, String> onComplete;

        private Builder() {
        }

        public Builder messages(String... messages) {
            this.messages = messages;
            return this;
        }

        public Builder onComplete(BiConsumer<Player, String> onComplete) {
            this.onComplete = onComplete;
            return this;
        }

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

ChatAskerExemplo.java

private final ChatAsker MULTIPLIER_ASKER = ChatAsker.builder()
            .messages("", "§a Digite o multiplicador de compra que você deseja", " §aselecionar.", " §aLembre-se que o seu limite é 64x.", " §aPara cancelar a ação digite \"cancelar\"", "")
            .onComplete((player, message) -> {
                if (message.equalsIgnoreCase("cancelar")) {
                    player.sendMessage("§eCancelado com sucesso.");
                }
                User user = manager.get(player.getName());
                int val = -1;
                try {
                    val = Integer.parseInt(message);
                    if (val <= 0) throw new Exception();
                } catch (Exception e) {
                    player.sendMessage("§cQuantidade inválida.");
                    return;
                }
                user.setMultiplier(val);
                player.sendMessage("§aMultiplicador de Compra definido com sucesso.");
            }).build();

MULTIPLIER_ASKER.addPlayer(player)