code: public static void validateGeoPackageExtension(File file) {
  		if (!hasGeoPackageExtension(file)) {
  			throw new GeoPackageException("GeoPackage database file '" + file
  					+ "' does not have a valid extension of '"
  					+ GeoPackageConstants.GEOPACKAGE_EXTENSION + "' or '"
  					+ GeoPackageConstants.GEOPACKAGE_EXTENDED_EXTENSION + "'");
  		}
  	}
docs: Validate the extension file as a GeoPackage
  
  @param file
  GeoPackage file