public List<ID> getNewMembers(GMSMembershipView<ID> olderView) {
    List<ID> result = new ArrayList<>(members);
    result.removeAll(olderView.getMembers());
    return result;
  }
return members that are i this view but not the given old view
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembershipView.java