Bukkit 1.20.1 插件：将两个小箱子合并为大箱子

以下代码实现了在 Bukkit 1.20.1 上将两个小箱子合并为大箱子的功能，并向玩家发送成功升级的消息：

import org.bukkit.Material;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.block.BlockPlaceEvent;
import org.bukkit.inventory.InventoryHolder;
import org.bukkit.block.Block;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;

public class ChestUpgradePlugin extends JavaPlugin implements Listener {

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

    @EventHandler
    public void onBlockPlace(BlockPlaceEvent event) {
        Player player = event.getPlayer();
        Block placedBlock = event.getBlockPlaced();
        
        if (placedBlock.getType() == Material.CHEST && placedBlock.getState() instanceof InventoryHolder) {
            InventoryHolder chest = (InventoryHolder) placedBlock.getState();
            
            // 检查放置的箱子是否为小箱子
            if (chest.getInventory().getSize() == 27) {
                Block adjacentBlock = placedBlock.getRelative(placedBlock.getFace(event.getBlockAgainst()));
                
                // 检查相邻方块是否为箱子
                if (adjacentBlock.getType() == Material.CHEST && adjacentBlock.getState() instanceof InventoryHolder) {
                    InventoryHolder adjacentChest = (InventoryHolder) adjacentBlock.getState();
                    
                    // 检查相邻的箱子是否为小箱子
                    if (adjacentChest.getInventory().getSize() == 27) {
                        // 将相邻的箱子升级为大箱子
                        adjacentBlock.setType(Material.CHEST);
                        adjacentChest.getInventory().setSize(54);
                        
                        player.sendMessage('成功将箱子升级为大箱子！');
                    }
                }
            }
        }
    }
}

请确保您的项目已经导入了 Bukkit 的依赖，并将以上代码保存为一个 Java 类文件。然后，将该类文件放置在您的插件项目中，并在插件的主类中注册该事件监听器。当玩家放置一个小箱子并在其旁边再放置一个箱子时，该插件将自动将相邻的箱子升级为大箱子，并向玩家发送一条消息。