public boolean addPlayer(Player player)
    {      
        //check if Player is persisted.  
        try {
            if ( pairs.size() < 2 )
            {          
                if (player.getId() == null) // not persisted yet
                {
                    //persist(player);
                    throw new Exception("Player should be persisted before adding to Pairing");
                }                      
                pairs.add(player);
                return true;
            }
            else
            { 
                throw new Exception("Cannot exceed two players per pairing");
            }
        } catch (Exception e) {e.printStackTrace();}
        return false;
    }