public List<Float> getDispersionInformation() {
    List<Float> dispersion = new ArrayList<>();
    dispersion.add(avgDispersionScore);
    dispersion.add(maxDispersionScore);
    dispersion.add(minDispersionScore);
    return dispersion;
  }
Return a list which contains 3 elements: average dispersion score, max dispersion score and min
dispersion score as first, second and third elements, respectively.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/AssignmentVerificationReport.java