if (oldValue == 0L) {
          // don't compareAndSet a zero
          if (map.replace(key, atomic, new AtomicLong(delta))) {
            return delta;
          }
          // atomic replaced
          continue outer;
        }

        long newValue = oldValue + delta;
        if (atomic.compareAndSet(oldValue, newValue)) {
          return newValue;
        }