private void loadReducedGroups() {
            if (this.reducedGroupSaveId != null && this.reducedGroupIdBackMapper != null) {
                final JsonNode node = JsonUtils.stringToNode(Settings.getSimpleListModelConfig(this.reducedGroupSaveId));
                if (node != null) {
                    final List<String> groupStrings = JsonUtils.getTextList(node, "groups");
                    setReducedGroups(groupStrings.stream().map(s -> this.reducedGroupIdBackMapper.apply(s)).collect(Collectors.toList()));
                }
            }
        }
Sets the  minimum number of groups on which grouping is really activated
main/src/main/java/cgeo/geocaching/ui/SimpleItemListModel.java