Re: Sharing Data Between App Instances

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 27 Dec 2006 22:42:21 GMT

Message-ID:

<hFCkh.3695$pQ3.2926@newsread4.news.pas.earthlink.net>

Mike wrote:

Forgive me; this is sort of a newbie question. Is it possible to share in-
memory data between instances of an app?

I realize I could just write the info to disk with one instance then read
it into the other instances from the disk, but I'd like to keep it in
memory for performance reasons.

This data may need to be accessed simultaneously by separate instances in a
read-only fashion. Only one instance will ever modify the data. It's
possible that attempts to read and update the data simultaneously may occur
so the code would need to support some type of locking.

Hopefully this question makes sense to someone besides me ;) Any code
needs to work on JVM version 1.4 (in case that matters.)

Thanks in advance! This group has been infinitely useful in my learning.
Hopefully soon I'll be able to contribute.

- Mike

Don't assume that every read of a shared file will cause a physical disk
read. Most operating systems do some disk caching, so frequently
accessed blocks may be in memory anyway.

Try whatever approach seems simplest first, and measure it. Make sure
you isolate the shared data access in your class design, so that the
implementation can be changed without rewriting the program.

Patricia