@Override
    public int compareTo(Delayed other) {
      // Delay is compared first. If there is a tie, compare region's hash code
      int ret =
        Long.valueOf(getDelay(TimeUnit.MILLISECONDS) - other.getDelay(TimeUnit.MILLISECONDS))
          .intValue();
      if (ret != 0) {
        return ret;
      }
      FlushQueueEntry otherEntry = (FlushQueueEntry) other;
      return hashCode() - otherEntry.hashCode();
    }
@param when When to expire, when to come up out of the queue. Specify in milliseconds. This
            method adds EnvironmentEdgeManager.currentTime() to whatever you pass.
@return This.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreFlusher.java