Re: Advice/Help with Multithreading

Knute Johnson <>
Tue, 16 Jan 2007 18:37:22 -0800
DyslexicAnaboko wrote:

I wrote a method that will take a URL, and return its page in String

Now depending on which webpage is being visited is how long it will
take to download its contents. There is a difference between getting
the contents of google vs. yahoo, obviously the page sizes differ.

Since I would have many pages to download, downloading them 1 at a time
takes forever. I just want to speed things up. I figured that
multithreading would be my answer since I could create several threads
to download pages simultaneously. I am inexperienced with
multithreading though, so I was just hoping that anyone could give me
some pointers or advice on where to begin.

Basically I want to do the following:

1. I want to create X threads, lets just say 10 for arguments sake.

2. I want each thread to get its own assigned URL. Will there be a
problem with more than one thread accessing the same method?

3. After downloading the contents of the page I intend to put the
strings into a list. Will there be a problem with more than one thread
accessing the same object? If so, should I use semaphores?

I'm not asking anyone to write this for me, I just don't know where to
begin. If anyone can spare an example or any advice I am all ears.



You can run the same method in multiple threads. Assuming that you
synchronize access to any variables that are accessed by multiple
threads. So if you write a method, getString(URL url) you can then
create a thread to run that method in as follows:

Runnable r = new Runnable() {
     public void run() {
new Thread(r).start();

You will need some code after the call to getString() to put it
somewhere but that is really all there is to it.

Start writing the program and post your progress.


Knute Johnson
email s/nospam/knute/

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