@Override
    public int hashCode() {
      int hash = (int) getDelay(TimeUnit.MILLISECONDS);
      return hash ^ region.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