public Map<String, List<ServerName>> getAssignmentMap() {
    // Make a deep copy so changes don't harm our copy of favoredNodesMap.
    return this.favoredNodesMap.entrySet().stream()
      .collect(Collectors.toMap(k -> k.getKey(), v -> new ArrayList<ServerName>(v.getValue())));
  }
Return the mapping between each region to its favored region server list.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/favored/FavoredNodesPlan.java