java 判断服务器地址的路径下文件是否存在

URL pathUrl = new URL(outputfilename);
HttpURLConnection urlcon = (HttpURLConnection) pathUrl.openConnection();
try{
    if(urlcon.getResponseCode()>=400){
        System.out.println("文件不存在");
    }
    else{
       System.out.println("文件不存在");
　　}