Java判断远程服务器上文件是否存在（跨服务器）

　          //方法一：
　　　　　  URL serverUrl = new URL("http://localhost:8090/Demo/clean.sql");
            HttpURLConnection urlcon = (HttpURLConnection) serverUrl.openConnection();

            String message = urlcon.getHeaderField(0);
            if (StringUtils.hasText(message) && message.startsWith("HTTP/1.1 404")) {
                System.out.println("不存在");
            }else{
                System.out.println("存在"+message);
            }
            
            //方法二：
            URL url = new URL("http://localhost:8090/Demo/clean.sql");
            HttpURLConnection urlcon2 = (HttpURLConnection) url.openConnection();
            Long TotalSize=Long.parseLong(urlcon2.getHeaderField("Content-Length"));  
            if (TotalSize>0){
                System.out.println("存在");
                
            }else{
                System.out.println("不存在");
            }