ClassNotFound err !

Hi !
I create a npc method, and there is an error

Code:

Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_8_R1.World

But I do not know how is it possible !
Can you help me ? (You'll maybe need my code !

Code:

        Location npcloc1 = new Location(
                Bukkit.getWorld("hub"),
                -1.5,
                6, -8.5,
                0, 0
        );
        MinecraftServer nmserv = ((CraftServer) Bukkit.getServer()).getServer();
        WorldServer nmsworld = ((CraftWorld) npcloc1.getWorld()).getHandle();
        this.npc = new EntityPlayer(nmserv, nmsworld, new GameProfile(UUID.randomUUID(), this.name), new PlayerInteractManager(nmsworld));
        this.npc.teleportTo(npcloc1, false);
        PlayerConnection pc = ((CraftPlayer) e.getPlayer()).getHandle().playerConnection;
        pc.sendPacket(new PacketPlayOutPlayerInfo(EnumPlayerInfoAction.ADD_PLAYER, this.npc));
        pc.sendPacket(new PacketPlayOutNamedEntitySpawn(this.npc));

 

If a 1.8 plugin doesn't causes error with a 1.8.3 server, yes