code: public static boolean isJarFileURL(URL url) {
  		return (URL_PROTOCOL_FILE.equals(url.getProtocol()) && //
  				url.getPath().toLowerCase().endsWith(FileUtil.JAR_FILE_EXT));
  	}
docs: 提供的URL是否为Jar文件URL 判断依据为file协议且扩展名为.jar
  
  @param url the URL to check
  @return whether the URL has been identified as a JAR file URL
  @since 4.1