private boolean needsBalanceIdleRegion(int[] cluster) {
    return Arrays.stream(cluster).anyMatch(x -> x > 1)
      && Arrays.stream(cluster).anyMatch(x -> x < 1);
  }
Data set for testLocalityCost: [test][0][0] = mapping of server to number of regions it hosts
[test][region + 1][0] = server that region is hosted on [test][region + 1][server + 1] =
locality for region on server
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancer.java