TDAT:     public void removeUser(User removableUser) throws FelperUserAddRemoveOperationException{
        if (this.users.remove(removableUser)) {
            if(logger.isDebugEnabled())
                logger.debug("User is Removed: " + removableUser);
        } else {
            logger.warn("Can`t remove user: " + removableUser);
            throw new FelperUserAddRemoveOperationException("Can`t remove user: " + removableUser);
        }
    }
 COM: <s> remove user and resize users array </s>