public boolean randPlaceBall(Graphics g, int aBallColor)
	{
		if (mEmptyPlace <= 0)	// ޿λ
		{
			return false;
		}
		
		int index = mRand.nextInt(mEmptyPlace);	// õλ,ǵڼλ,ɱ֤ȶ
		for (int i=0; i<FaceStyle.BALL_HNUM; i++)	// ҵλ
		{
			for (int j=0; j<FaceStyle.BALL_VNUM; j++)
			{
				if (mWhatBall[i][j] == BallColor.EMPTY)
				{
					if (index == 0)
					{
						mWhatBall[i][j] = aBallColor;
						mEmptyPlace--;	// λһ
						drawBallCheck(g, aBallColor, 0, i, j);	// 
						return true;	// ɹ
					}
					index--;
				}
			}
		}
		
		return false;	// ޿λ
	}