Code

enum RectSide
{
	LEFT {
		float dist(PointF point, RectF rect) { return Math.abs(point.x - rect.left); }
	},
	TOP {
		float dist(PointF point, RectF rect) { return Math.abs(point.y - rect.top); }
	},
	RIGHT {
		float dist(PointF point, RectF rect) { return Math.abs(point.x - rect.right); }
	},
	BOTTOM {
		float dist(PointF point, RectF rect) { return Math.abs(point.y - rect.bottom); }
	};

	static RectSide fromPoint(PointF point, RectF rect)
	{
		float minDist = Float.MAX_VALUE;
		RectSide closest = LEFT;

		for (RectSide side: values())
		{
			float dist = side.dist(point, rect);
			if (dist < minDist)
			{
				minDist = dist;
				closest = side;
			}
		}

		return closest;
	}

	abstract float dist(PointF point, RectF rect);
}