URL中的上次修改日期

Question

I'm writing client socket code in java and I found this piece of code which is supposed to read a line and check last modified date.

I am confused why does it need to subtract the length by 21 in the modDateArr?

And is there any other way to do this?

while((x = br.readLine()) != null){
    if(x.contains("Last-Modified:")){
        modDateArr = new char[x.length()-21];
        x.getChars(20, x.length()-1, modDateArr, 0);
         // create mod date string from last mod info
        modDate = new String(modDateArr);
        break;
    }
}

Answer 1

Yes there is a better way: use URL and URLConnection :

URL url = new URL("http://blablah/foo");
URLConnection connection = url.openConnection();
Date lastModified = new Date(connection.getLastModified());

Note that the Last-Modified header looks like this:

Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT

If you remove the first 21 characters from that line like your code does, you get this: 15 Nov 1995 04:58:08 GMT .