From Doug Lea's TODO list:

2. Clocks and improved CyclicBarriers
    A "Clock" (not a good name but that's what the X10 folks call it,
    so the name will probably stick) is just like a CountDownLatch
    except (1) it sometimes allows counts to be incremented (2) it can
    contain nested Clocks that it must wait out. It can/should be
    implemented as extensions of scalable counters. As can an
    overhaul of CyclicBarrier (Bill and I think we know how.)