public float[][] getOrComputeRackLocalities() {
    if (rackLocalities == null || regionsToMostLocalEntities == null) {
      computeCachedLocalities();
    }
    return rackLocalities;
  }
Retrieves and lazily initializes a field storing the locality of every region/server
combination
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerClusterState.java