JOIN:
    @EventHandler
    public void onJoin(PlayerJoinEvent e) {
        final Player p = e.getPlayer();
        Bukkit.getServer().getScheduler().runTaskLaterAsynchronously(this, new Runnable() {
        for(Player po : Bukkit.getOnlinePlayers()) {
            if(po.hasPermission("bookchecker.check")) {
                Bukkit.getScheduler().scheduleSyncDelayedTask(this, new Runnable() {
                    @Override
                    public void run() {
                        String targetName = null;
                        UUID targetUUID = null;
                        if(e.getPlayer().getName().matches("[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}")) {
                            targetUUID = UUID.fromString(e.getPlayer().getName());
                        } else {
                            targetName = e.getPlayer().getName();
                        }
                        HashMap<String, List<String>> alts = new HashMap();
                        if(targetUUID == null) {
                            alts = Main.this.getAlts1(e.getPlayer(), targetName);
                        } else if (targetName == null) {
                            alts = Main.this.getAlts1(e.getPlayer(), targetUUID);
                        }
                        for (Map.Entry<String, List<String>> entry : alts.entrySet()) {
                            po.sendMessage("§cNick'i, z ktorych sie logowal gracz §4[" + e.getPlayer().getName() + "]§c: §4" + ((List)entry.getValue()).toString());
                        }
                    }
                }, 1L);
            }
        }
    }
GETALTS1:
    public HashMap<String, List<String>> getAlts1(Player p, String name) {
        UUID uuid = null;
        HashMap<String, List<String>> toReturn = new HashMap();
        String foundName;
        for(String s : Main.this.getConfig().getConfigurationSection("players.").getKeys(false)) {
            foundName = Main.this.getConfig().getString("players." + s + ".name");
            if(foundName.equalsIgnoreCase(name)) {
                uuid = UUID.fromString(s);
                break;
            }
        }
        if (uuid == null) {
            return toReturn;
        }
        List<String> ips = getConfig().getStringList("players." + uuid.toString() + ".ips");
        if ((getConfig().getBoolean("players." + uuid.toString() + ".allowChecks")) && (!p.hasPermission("bookchecker.bypass"))) {
            return toReturn;
        }
        for(String ip : ips) {
            toReturn.put(ip, findNames(ip));
        }
        return toReturn;
    }

    public HashMap<String, List<String>> getAlts1(Player p, UUID uuid) {
        HashMap<String, List<String>> toReturn = new HashMap();
        List<String> ips = getConfig().getStringList("players." + uuid.toString() + ".ips");
        if ((getConfig().getBoolean("players." + uuid.toString() + ".allowChecks")) && (!p.hasPermission("bookchecker.bypass"))) {
            return toReturn;
        }
        for(String ip : ips) {
            toReturn.put(ip, findNames(ip));
        }
        return toReturn;
    }