a

    Long time = plugin.getConfig().getLong("combatTagTime") * 60;

    @EventHandler
    public void onHit(EntityDamageByEntityEvent e){
        if(e.getDamager() instanceof Player){
            final Player p = (Player) e.getEntity();
            if(!list.containsKey(p.getName())){
                if(!combatTag.containsKey(p.getName())){
                    combatTag.put(p.getName(), true);
                    Bukkit.getScheduler().runTaskLater(plugin, new Runnable() {
                        @Override
                        public void run() {
                            combatTag.remove(p.getName());
                        }
                    }, time); // if i put this long "time" here, it does not work.
                }