Hier mein Jetziger Code:

package de.mischmaschine.util;
import org.bukkit.Bukkit;
import org.bukkit.Material;
import org.bukkit.enchantments.Enchantment;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;

public class KnockUtil {

    @EventHandler
    public void OnJoinEvent(PlayerJoinEvent e) {
        Player p = e.getPlayer();
        ItemStack stick = new ItemStack(Material.STICK);
        p.getInventory().addItem(stick);;
        stick.addEnchantment(Enchantment.KNOCKBACK, 2);
        ItemStack item = new ItemStack(Material.STICK, 1);
        ItemMeta meta = item.getItemMeta();
        meta.setDisplayName("§a§lKnüppel");
        item.setItemMeta(meta);
        p.getInventory().setItem(0, item);
        e.setJoinMessage("");
    }

    @SuppressWarnings("deprecation")
    public static String getUUIDbyName(String name) {
        return Bukkit.getOfflinePlayer(name).getUniqueId().toString();
    }
}

Was genau funktioniert hier nicht?