Java下载文件前通过HTTP请求获取文件大小

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Java下载文件前通过HTTP请求获取文件大小

/**
* 获取网络文件大小 
*/
private static long getFileLength(String downloadUrl) throws IOException{if(downloadUrl == null || "".equals(downloadUrl)){return 0L ; }URL url = new URL(downloadUrl);HttpURLConnection conn = null;try {conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("HEAD");conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows 7; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.73 Safari/537.36 YNoteCef/5.8.0.1 (Windows)");return (long) conn.getContentLength();} catch (IOException e) {return 0L;} finally {conn.disconnect();}
}