The code snippet presented below shows how to check if a web page exists not not.

Java Code:
public class URLUtils {

  public static void main(String s[]) {
    System.out.println(URLUtils.exists
    ("http://www.java-forums.org/howto.html"));
    System.out.println(URLUtils.exists
    ("http://www.java-forums.org/pagenotfound.html"));
    /*
      output :
        true
        false
    */    
  }

  public static boolean exists(String URLName){
    try {
      HttpURLConnection.setFollowRedirects(false);
      // note : you may also need
      //        HttpURLConnection.setInstanceFollowRedirects(false)
      HttpURLConnection con =
         (HttpURLConnection) new URL(URLName).openConnection();
      con.setRequestMethod("HEAD");
      return (con.getResponseCode() == HttpURLConnection.HTTP_OK);
    }
    catch (Exception e) {
       e.printStackTrace();
       return false;
    }
  }
}