@Override
  public String[] getCombinedGroups() {
    ArrayList<String> groupList = new ArrayList<>();
    if (includeMembershipGroups) {
      for (String g : MemberDataBuilder.parseGroups(null, getSystem().getConfig().getGroups())) {
        if (!groupList.contains(g)) {
          groupList.add(g);
        }
      }
    }
    for (String g : getGroups()) {
      if (!groupList.contains(g)) {
        groupList.add(g);
      }
    }
    String[] groups = new String[groupList.size()];
    return groupList.toArray(groups);
  }
Returns an array of all the groups of this cache server. This includes those from the groups
gemfire property and those explicitly added to this server.
geode-core/src/main/java/org/apache/geode/internal/cache/CacheServerImpl.java