public Node getNode(Coordinate coordinate)
	{
		if (coordinate.getY() < 0 || coordinate.getY() >= nodeMatrix.size())
		{
			return null;
		}
		else if (coordinate.getX() < 0 || 
				coordinate.getX() >= nodeMatrix.get(coordinate.getY()).size())
		{
			return null;
		}
		else
		{
			return this.nodeMatrix.get(coordinate.getY()).get(coordinate.getX());
		}
	}