Url.openstream():strange result of available().

Question

I test my first network programming,and the result is very strange,It seems that the result of available() is random!
URL url= new URL("ftp://ftp.pku.edu.cn/pub/proxy.txt");
InputStream is=url.openStream();
/***** the output is 0 ********/
System.out.println(is.available());
URL url1= new URL("ftp://ftp.pku.edu.cn/pub/proxy.txt");          is=url1.openStream();
/******* the result is 4092 ************/
     System.out.println(is.available());
Why this happen? the result should be equal!

Answer 1

is that the exact code that shows those results? anyway, it doesn't matter, available() is not random, it just may return different values as it reads in more bytes, so if the other send keeps sending data, available() will keep returning larger and larger values!
perhaps the first time the connection with a little slow, the server may not have responded very quickyl, or the underlying buffer might not have been full enough so it didn't flush it out to you, in any case, available() is not random.