Re: Distinct ID Number Per Object?

From:

Hal Vaughan <hal@thresholddigital.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 16 Jun 2007 19:25:59 -0400

Message-ID:

<ytydnYibweYY7OnbnZ2dnUVZ_jOdnZ2d@comcast.com>

Twisted wrote:

....

public class Base {
    public final long id; // should stay unique even on 64-bit
architectures, or with long running systems
    private static long idGenerator;
    public Base () {
        synchronized (Base.class) {
            id = idGenerator;
            idGenerator++;
        }
    }
    ...
}

There may be nothing to this, but, as I've said in this thread before, and
said on this group many times, being self taught, I know there are many
things I've missed. Is there any particular reason for you using this:

      id = idGenerator;
      idGenerator++;

Instead of this:

      id = idGenerator++;

If you don't construct Base instances in more than one thread at a
time, you can dump the synchronization. Otherwise it is needed to
prevent race conditions with accessing and incrementing idGenerator,
which could result in two objects getting the same id at the same
time, and the next id in sequence being skipped.

While this is working with Swing, all the objects are created before the
first interactive window opens, so, no, race conditions are not an issue.

Hal