code: public static BoundingBox getBoundingBox(int x, int y, int zoom) {
  
  		int tilesPerSide = tilesPerSide(zoom);
  		double tileWidthDegrees = tileWidthDegrees(tilesPerSide);
  		double tileHeightDegrees = tileHeightDegrees(tilesPerSide);
  
  		double minLon = -180.0 + (x * tileWidthDegrees);
  		double maxLon = minLon + tileWidthDegrees;
  
  		double maxLat = 90.0 - (y * tileHeightDegrees);
  		double minLat = maxLat - tileHeightDegrees;
  
  		BoundingBox box = new BoundingBox(minLon, minLat, maxLon, maxLat);
  
  		return box;
  	}
docs: Get the tile bounding box from the Google Maps API tile coordinates and
  zoom level
  
  @param x
  x coordinate
  @param y
  y coordinate
  @param zoom
  zoom level
  @return bounding box