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We had an outstanding presentation at the St. Louis JUG yesterday evening. Eric Burke, of the It's Just a Bunch of Stuff That Happens fame, gave a presentation on some of the new Java 5 and 6 concurrency features, through a series of examples. Like in the past, this is another one of those "you have to be there to experience it" presentations.

Here's what I learned from this presentation:

• The Java Concurrency in Practice book, by Brian Goetz, with Tim Peierls, Joshua Bloch, Joseph Bowbeer, David Holmes, and Doug Lea, is a must read for anyone developing Java applications on a modern Java platform.
• Have you written something like this

  try {
    Thread.sleep(1000);
  } catch (InterruptedException e) {
    // ignored
  }

  This is completely wrong.
• i++ is not atomic.
• The new concurrency utilities package in Java 5 and 6 is very rich. It's worth studying in depth.
• TimeUnit
• CopyOnWriteArraySet
• Use a ThreadFactory to create threads and give them proper names instead of the default "Thread-1", "Thread-2" and register UncaughtExceptionHandler's.
• Executor, Future
• Lock, tryLock(), lockInterruptibly()
• ReadWriteLock
• BlockingQueue
• Here's how a thread should be written

  new Thread() {
    public void run() {
      while (!Thread.currentThread().isInterrupted()) {
        // do the work...
      }
    }
  }

At the meta level, I think the lesson is there are so much stuff that's new in Java 5, that it's worth learning it anew.

On a different topic in the post presentation chats, Eric mentioned that the latest Java 6 have many improvements over Java 5. And if you are upgrading from Java 1.4, you might as well skip Java 5 and jump directly to Java 6