If in the URLconnection I setUseCaches(true), I must to wait until...

Question

Hello, sorry for my english and thanks for all.
I know how can to use an URLconnection for to get the file size for download and after to get the InputStream read it and to get the progress download.
If in the URLconnection I setUseCaches(true), I must to wait until the file is all download an after I can read the InputStream.
If in the URLconnection I setUseCaches(false), I can read the InputStream at the same time that the file is downloading.
I have two questions:
- if I setUseCaches(true), why I must to wait until the file is all download an after I can read the InputStream?
- how can I get the progress download if setUseCaches(true) in the URLconnection?
very thanks

Answer 1

This is the code that I've used:
try{
     URLConnection urlconnection;
     urlconnection = (new URL(getDocumentBase(), "beni0271.jpg")).openConnection()
     urlconnection.setUseCaches(true);
     //If in the URLconnection I setUseCaches(true), I must to wait until the file is all download an after I can read the InputStream.
     //If in the URLconnection I setUseCaches(false), I can read the InputStream at the same time that the file is downloading.
     System.out.println(urlconnection);
     length =     urlconnection.getContentLength();
     inps = urlconnection.getInputStream();
     System.out.println(inps);
}catch(MalformedURLException e){
     System.out.println(e);
}catch(IOException e){
     System.out.println(e);
}