Java文件下载乱码问题

public static String decode(String userAgent, String fileName) throws Exception {
if (userAgent.indexOf("MSIE") >= 0) {
return URLEncoder.encode(fileName, "UTF8");// IE
} else if (userAgent.indexOf("Mozilla") >= 0) {
return new String(fileName.getBytes("UTF-8"), "ISO-8859-1");// chrome,火狐，Safari
} else {
return URLEncoder.encode(fileName, "UTF8");// 其他浏览器
}
}