How to check if a URL exists or returns 404 with Java

Question

String urlString    http   www nbc com Heroes novels downloads Heroes novel 001 pdf   URL url   new URL urlString   if    Url does not return 404           System out println  exists      else       System out println  does not exists      urlString    http   www nbc com Heroes novels downloads Heroes novel 190 pdf   url   new URL urlString   if    Url does not return 404           System out println  exists      else       System out println  does not exists        This should print  exists does not exists   TEST  public static String URL    http   www nbc com Heroes novels downloads     public static int getResponseCode String urlString  throws MalformedURLException  IOException       URL u   new URL urlString        HttpURLConnection huc     HttpURLConnection   u openConnection         huc setRequestMethod  GET         huc connect         return huc getResponseCode       System out println getResponseCode URL    Heroes novel 001 pdf      System out println getResponseCode URL    Heroes novel 190 pdf        System out println getResponseCode  http   www example com      System out println getResponseCode  http   www example com junk                  Output  200 200 200 404  SOLUTION  Add the next line before  connect   and the output would be 200  404  200  404  huc setRequestProperty  User-Agent    Mozilla 5 0  Windows  U  Windows NT 6 0  en-US  rv 1 9 1 2  Gecko 20090729 Firefox 3 5 2   NET CLR 3 5 30729

User · Answer

There is nothing wrong with your code  It s the NBC com doing tricks on you  When NBC com decides that your browser is not capable of displaying PDF  it simply sends back a webpage regardless what you are requesting  even if it doesn t exist   You need to trick it back by telling it your browser is capable  something like   conn setRequestProperty  User-Agent        Mozilla 5 0  Macintosh  U  Intel Mac OS X 10 5  en-US  rv 1 9 0 13  Gecko 2009073021 Firefox 3 0 13

User · Answer

Use HttpUrlConnection by calling openConnection   on your URL object   getResponseCode   will give you the HTTP response once you ve read from the connection   e g      URL u   new URL  http   www example com         HttpURLConnection huc    HttpURLConnection u openConnection        huc setRequestMethod  GET        huc connect         OutputStream os   huc getOutputStream        int code   huc getResponseCode        not tested

User · Answer

this worked for me    URL u   new URL    http   www example com     HttpURLConnection huc      HttpURLConnection    u openConnection      huc setRequestMethod   GET       OR  huc setRequestMethod   HEAD     huc connect       int code   huc getResponseCode     System out println code     thanks for the suggestions above

User · Answer

Based on the given answers and information in the question  this is the code you should use   public static boolean doesURLExist URL url  throws IOException          We want to check the current URL     HttpURLConnection setFollowRedirects false        HttpURLConnection httpURLConnection    HttpURLConnection  url openConnection            We don t need to get data     httpURLConnection setRequestMethod  HEAD            Some websites don t like programmatic access so pretend to be a browser     httpURLConnection setRequestProperty  User-Agent    Mozilla 5 0  Windows  U  Windows NT 6 0  en-US  rv 1 9 1 2  Gecko 20090729 Firefox 3 5 2   NET CLR 3 5 30729         int responseCode   httpURLConnection getResponseCode            We only accept response code 200     return responseCode    HttpURLConnection HTTP OK      Of course tested and working

User · Answer

You may want to add   HttpURLConnection setFollowRedirects false      note   or           huc setInstanceFollowRedirects false    if you don t want to follow redirection  3XX    Instead of doing a  GET   a  HEAD  is all you need   huc setRequestMethod  HEAD    return  huc getResponseCode      HttpURLConnection HTTP OK

[java] How to check if a URL exists or returns 404 with Java?

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