@Override
    public int compareTo(Delayed o) {
      long cmp = getDelay(TimeUnit.MILLISECONDS) - o.getDelay(TimeUnit.MILLISECONDS);
      return cmp == 0 ? 0 : (cmp < 0 ? -1 : 1);
    }
A blocking queue implementation for adding a constant delay. Uses a DelayQueue as a backing store
@param <E> type of elements
hbase-server/src/test/java/org/apache/hadoop/hbase/util/ConstantDelayQueue.java