private List<HRegionServer> getOnlineRegionServers() {
    List<HRegionServer> list = new ArrayList<>();
    for (JVMClusterUtil.RegionServerThread rst : UTIL.getHBaseCluster().getRegionServerThreads()) {
      if (rst.getRegionServer().isOnline()) {
        list.add(rst.getRegionServer());
      }
    }
    return list;
  }
Determine if regions are balanced. Figure out the total, divide by the number of online
servers, then test if each server is +/- 1 of average rounded up.
hbase-server/src/test/java/org/apache/hadoop/hbase/TestRegionRebalancing.java