public Player getRealPlayer() throws RealPlayerException {
		Player playerFound = null;
		for (Player p:players) {
			if (p instanceof RealPlayer) {
				if(playerFound != null) {
					throw new RealPlayerException("there are several RealPlayers !");
				}
				else {
					playerFound = p;
				}
			}
		}
		if (playerFound == null) {
			throw new RealPlayerException("no RealPlayer found !");
		}
		return playerFound;
	}