Java-CommandSender类型未定义适用于此的getName（Object）

Question

我遇到此错误：

这是该行中的代码错误：

  sender.sendMessage(ConfigurationService.GRAY + Joiner.on(", ").join((Iterable)playerList.stream().map((Function<? super Object, ?>)CommandSender::getName).collect((Collector<? super Object, ?, List<? super Object>>)Collectors.toList())));

完整代码

public class NearCommand implements CommandExecutor
{
    public static final int RADIUS = 30;
    private final HCF hcf;

    public NearCommand(final HCF hcf) {
        this.hcf = hcf;
    }

    public boolean onCommand(final CommandSender sender, final Command cmd, final String label, final String[] args) {
        if (sender instanceof Player) {
            final Player player = (Player)sender;
            final List<Player> playerList = this.getNearbyEnemies(player);
            if (playerList.isEmpty()) {
                sender.sendMessage(ConfigurationService.YELLOW + "There are no visible enemies in a " + 30 + " block radius");
            }
            else {
                sender.sendMessage(ConfigurationService.YELLOW + "Nearby visible enemies in a " + 30 + " block radius");
                sender.sendMessage(ConfigurationService.GRAY + Joiner.on(", ").join((Iterable)playerList.stream().map((Function<? super Object, ?>)CommandSender::getName).collect((Collector<? super Object, ?, List<? super Object>>)Collectors.toList())));
            }
        }
        else {
            sender.sendMessage(ConfigurationService.RED + "You need to be a player to do this");
        }
        return true;
    }

    public List<Player> getNearbyEnemies(final Player player) {
        final List<Player> players = new ArrayList<Player>();
        final FactionManager factionManager = this.hcf.getFactionManager();
        final Faction playerFaction = factionManager.getPlayerFaction(player.getUniqueId());
        final Collection<Entity> nearby = (Collection<Entity>)player.getNearbyEntities(30.0, 30.0, 30.0);
        for (final Entity entity : nearby) {
            if (entity instanceof Player) {
                final Player target = (Player)entity;
                if (!target.canSee(player)) {
                    continue;
                }
                if (!player.canSee(target)) {
                    continue;
                }
                if (target.hasPotionEffect(PotionEffectType.INVISIBILITY)) {
                    continue;
                }
                final Faction targetFaction;
                if (playerFaction != null && (targetFaction = factionManager.getPlayerFaction(target)) != null && targetFaction.equals(playerFaction)) {
                    continue;
                }
                players.add(target);
            }
        }
        return players;
    }

这是bukkit的子句 我需要帮助。