code: public void initialize(Configuration conf, FSClusterStats stats,
        NetworkTopology clusterMap, HostsFileReader hostsReader,
        DNSToSwitchMapping dnsToSwitchMapping, FSNamesystem ns) {
      super.initialize(conf, stats, clusterMap, hostsReader, dnsToSwitchMapping, ns);
      this.rackWindow = conf.getInt("dfs.replication.rackwindow", 2);
      this.machineWindow = conf.getInt("dfs.replication.machineWindow", 5);
      this.racks = new ArrayList<String>();
      this.hostsReader = hostsReader;
      this.dnsToSwitchMapping = dnsToSwitchMapping;
      hostsUpdated(true);
      if (r == null) {
        r = new Random();
      }
      LOG.info("BlockPlacementPolicyConfigurable initialized");
    }
docs: {@inheritDoc}