@Override
  protected CandidateGenerator getRandomGenerator(BalancerClusterState cluster) {
    Class<? extends CandidateGenerator> clazz = shuffledGeneratorClasses.get()
      .get(ThreadLocalRandom.current().nextInt(candidateGenerators.size()));
    return candidateGenerators.get(clazz);
  }
Returns any candidate generator in random
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/FavoredStochasticBalancer.java