Re: My (lack of )wisdom about threads

Tom Anderson <>
Sun, 24 May 2009 12:28:58 +0100
On Sat, 23 May 2009, Joshua Cranmer wrote:

Stefan Ram wrote:

  So, inspired by ?Swing application architecture question.?, here is
  my (lack of )wisdoms about threads:

    - To correctly use multi-threading, a special education is needed.
      I do not yet have taken the time to undergo this, so I need
      to refrain from using threads (that is, more than one thread).

I wouldn't say that special education is needed at Java's level of
abstraction. I've been able to do it to some degree, and I certainly never
had it yet. If you know what synchronized does and when you might want to use
volatile, you'll probably be fine. Java 5 and 6 (and possibly 7) introduce
new concurrency utilities that eases some use, especially if you have a lot
of threads interacting.

Some of them also make life more complicated, because you have more

I do like AtomicBoolean, though. It lets you implement something that's
like an optional synchronized block. Rather than:

private final Object lock = new Object();

synchronized (lock) {

You do:

private final AtomicBoolean lock = new AtomicBoolean();

if (lock.compareAndSet(false, true)) {
  try {
  finally {

This still guarantees mutual exclusion, but means that if a second thread
comes along while a first thread is in the critical section, rather than
blocking, it skips over the critical section. I used this construct to
guard some housekeeping work in a multithreaded program; something that
needs to be done quite often, but must only be done by one thread.


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