Question

Using java.net, java.io, what is the fastest way to parse html from online, and load it to a file or the console? Is buffered writer/buffered reader faster than inputstreamreader/outputstreamwriter? Are writers and readers faster than outputstreams and inputstreams?
I am experiencing serious lag with the following output writer/stream:

URLConnection ii;
BufferedReader iik = new BufferedReader(new InputStreamReader(ii.getInputStream()));

String op;

while(iik.readLine()!=null) {
    op=iik.readLine();
    System.out.println(op);
}   

But curiously i am experiencing close to no lagtime with the following code:

URLConnection ii=i.openConnection();
Reader xh=new InputStreamReader(ii.getInputStream());

int r;
Writer xy=new PrintWriter(System.out);

while((r=xh.read())!=-1) {
    xy.write(r);
}  

xh.close();
xy.close();

What is going on here?

Answer 1

Readers/Writers shouldn’t be inherently faster than Input/OutputStreams.

That said, going through readLine() and println() probably isn’t the optimal way of transferring bytes. In your case, if the file you’re loading doesn’t contain many newline characters, BufferedReader will have to buffer a lot of data before readLine() will return.

The canonical non-terrible way of transferring data between streams is doing it in chunks by using a buffer:

byte[] buf = new byte[1<<12];
InputStream in = urlConnection.getInputStream();
int read = -1;

while ((read = in.read(buf) != -1) {
    System.out.write(buf, 0, read);
}

It might be faster yet to use NIO, the code for it is a little less straightforward and I just use the one found in this blog post.

If you’re writing to/from a file, the best method is to use a zero-copy approach, which Java makes available with FileChannel.transferFrom() and transferTo(). Sample code is available in a DeveloperWorks article.