Re: Multi-threading: wait for tasks to complete

Peter Duniho wrote:


Thanks for the feedback. I was hoping that synchronized methods in
UpDownLatch could be optimized to spin-locks at runtime, thus saving the
overhead of either a full lock or using AtomicInteger. However, I
haven't profiled it yet so I'm not sure that the synchronized methods
are better. It's certainly worthy of investigation.

I'd probably modify your idea as follows to avoid the explicit lock
object; the AtomicInteger can serve the same purpose (code is untested):

    private static class UpDownLatch2
    {
       private AtomicInteger count = new AtomicInteger();
       public void countUp() {
          count.incrementAndGet();
       }
       public void countDown() {
          synchronized( count ) {
             if( count.decrementAndGet() == 0 ) {
                count.notifyAll();
             }
          }
       }
       public void await() throws InterruptedException {
          synchronized( count ) {
             while( count.get() != 0 ) {
                count.wait();
             }
          }
       }
    }